Stormwater Management PlanMEMORANDUM
December 13, 2001
TO:
FROM:
SUBJECT:
The Honorable Mayor and City Council Members
Michael C. Van Milligen, City Manager
Stormwater Management Plan
In 1996, the City of Dubuque, through the Capital Improvement Project Budget,
committed to developing a City-wide Stormwater Management Plan. The need for the
plan arose from a growing number of citizen complaints related to stormwater runoff and
that need was intensified with the significant amount of damage to hundreds of homes
in a major rainstorm in May 1999. Increasing public safety and reducing property
damage are the primary goals of the Stormwater Management Plan.
HDR Engineering, Inc. of Omaha, Nebraska, was the selected consulting engineering
firm to produce Dubuque's Stormwater Management Plan. The Stormwater
Management Plan consists of four elements:
A Drainage Basin Master Plan that addresses flooding problems and issues in
specific watershed basins;
A Stormwater Drainage Criteria Manual that guides development to prevent new
drainage problems and reduce pollution associated with stormwater runoff;
A set of ordinances and policies that specifically address stormwater runoff
issues; and
A skeleton National Pollution Discharge Elimination System Phase II permit
application to be refined by City staff.
To achieve the primary objective of increasing public safety and reducing property
damage related to stormwater runoff, the following steps were followed:
Determine the capacity of the existing drainage system for the 10-, 50-, 100- and
500-year return period storm events under future drainage basin characteristics;
Develop hydrologic and hydraulic models using aerial topographic system
mapping using the Dubuque Area Geographical Information System (DAGIS) for
major drainage segments within each watershed;
Identify areas where public safety is comprised and property damage occurs due
to stormwater runoff; and
Identify funding sources that might be available to construct the recommended
drainage improvements identified by the Basin Master Plan.
Assistant City Engineer Gus Psihoyos and Civil Engineer Deron Muehring are
recommending adoption of the Drainage Basin Master Plan, as previously presented to
the Mayor and City Council in a public Work Session, and subsequently presented to
interested parties. The Plan recommends $24.1 million in construction projects for
improvements that will remove over 1,200 homes and businesses from risk of flood
damage from heavy rainfall events. The improvements include:
1. North Fork Catfish Creek Basin improvements - $2,135,300
2. West 32nd Street Sub-basin improvements - $4,898,000
3. Bee Branch Creek restoration - $17,100,000
The recommended modifications to the Northwest Arterial Detention Basin have been
previously approved and were implemented this fiscal year.
The most significant cost item in this recommendation is the $17.1 million for the Bee
Branch Creek Restoration Project. The creation of an open channel, beginning at 24th
and Elm Streets, and extending to the 16th Street Detention Basin, would eliminate the
risk of flood damage to 970 homes and businesses. The cost of the channel includes
the purchase of approximately 70 homes and businesses.
Historically, the Bee Branch Creek meandered through the north end. Over the years
the creek was lined by limestone, eventually covered, and transformed into the existing
Bee Branch Storm Sewer. The proposed channel is, in reality, the restoration of the
Bee Branch Creek. With a 76' bottom width, the channel would be designed with mildly
sloping landscaped banks. It is anticipated that a 150' green corridor would be required
for the channel. The exact alignment of the channel is yet to be determined. Part of
this recommendation includes issuing a request for proposals for a corridor study to
establish the alignment of the Bee Branch Basin Flood Control Channel recommended
in this report.
An alternative to constructing this channel was studied and it was determined that five
additional underground storm sewer systems, the size of the existing Bee Branch Storm
Sewer, which is 20' wide and 12' high at its largest point, would need to be constructed
at a cost exceeding $90 million. Therefore, this underground option is not being
recommended.
The City of Dubuque does not currently have the funding capacity to pay for these
improvements, totaling over $24 million. Therefore, through the City's Fiscal Year 2003
budgeting process, the Council will be receiving a recommendation to form a
stormwater utility to fund the stormwater activities of the City, and in addition, the City
will need to pursue federal funding in support of these projects.
I concur with the recommendations and respectfully request Mayor and City Council
approval.
I further respectfully request that the Long Range Planning Advisory Commission be
assigned to lead a community planning effort to implement the Stormwater
Management Plan, working to mitigate any impacts on individuals and neighborhoods,
and providing input on the formation of a Stormwater Management Utility to finance the
implementation of the plan. Part of the direction of the Long Range Planning Advisory
Commission would be to formulate a City Interest Group that will be comprised of
potentially-impacted property owners and businesses, as well as representatives from
such areas as neighborhood associations, the Environmental Stewardship Advisory
Commission, the Housing Commission, the Community Development Advisory
Commission, school, real estate, health officials, civic leaders and church organizations.
The key staff members I will be assigning to work with the commission are Planning
Services Manager Laura Carstens, Housing and Community Development Director
David Harris and Assistant City Engineer Gus Psihoyos.
Michael C. Van Milligen
MCVM/jh
Attachment
CC:
Barry Lindahl, Corporation Counsel
Cindy Steinhauser, Assistant City Manager
Laura Carstens, Planning Services Manager
David Harris, Housing and Community Development Director
Gus Psihoyos, Assistant City Engineer
Deron Muehring, Civil Engineer
CITY OF DUBUQUE, IOWA
MEMORANDUM
December 11, 2001
TO:
FROM:
SUBJECT:
Michael C. Van Milligen, City Manager
Gus Psihoyos, Assistant City Engineer
Deron Muehring, Civil Engineer
Stormwater Management Plan
INTRODUCTION
The attached resolution provides for:
1)
2)
Adoption of the City of Dubuque Drainage Basin Master Plan (DBMP)
prepared by HDR Engineering, Inc.; and
Authorization to prepare a Request for Proposals (RFP) for a corridor
study to establish the alignment of the Bee Branch basin flood control
channel recommended in the DBMP.
BACKGROUND
In 1996, the City of Dubuque, through the Capital Improvement Project Budget,
committed to developing a City-wide Stormwater Management Plan. The need
for the plan arose from a growing number of citizen complaints related to
stormwater runoff and the significant amount of damage to hundreds of homes in
a major rainstorm in May, 1999. Increasing public safety and reducing property
damage are the primary goals of the Stormwater Management Plan.
In 1997, six consulting engineering firms formally submitted proposals to prepare
a plan for the City. After a second interview the team of engineers headed by
HDR Engineering, Inc. of Omaha, Nebraska was selected to produce Dubuque's
Stormwater Management Plan.
The Stormwater Management Plan consists of four elements:
A Drainage Basin Master Plan that addresses flooding problems
and issues in specific watershed basins;
A Stormwater Drainage Criteria Manual that guides development to
prevent new drainage problems and reduce pollution associated
with stormwater runoff;
3. A set of ordinances and policies that specifically address
stormwater runoff issues; and
4. A skeleton NPDES Phase II permit application to be refined by City
Staff.
The accompanying document is the Drainage Basin Mater Plan, prepared by
HDR Engineering, for the Bee Branch and North Fork Catfish Creek watersheds
(see Figure 1). It should be emphasized that the Drainage Basin Master Plan
does not identify all areas within the City that experience poor drainage. In fact,
many drainage problems are of a localized nature. The City will continue to
investigate all drainage complaints on an individual basis, assess whether the
master plan addresses such issues, and assist property owners in any way
possible to reduce the impacts of stormwater runoff. The remaining tasks will be
completed during the winter of 2001-2002.
DISCUSSION
A master plan is a plan for an entire watershed. When a modification is made to
a portion of a watershed's drainage pattern it usually effects, for better or worse,
the drainage of the entire watershed. The Drainage Basin Master Plan is
necessary to ensure that efforts to solve stormwater problems are efficient and
cost-effective and address the concerns of taxpayers and drainage system users.
To achieve the primary objective-increasing public safety and reducing property
damage related to stormwater runoff-the following steps were followed:
Determine the capacity of the existing drainage system for the 10-,
50-, 100- and 500-year return period storm events under future
drainage basin characteristics;
Develop hydrologic and hydraulic models using aerial topographic
mapping using the Dubuque Area Geographical Information
System (DAGIS) for major drainage segments within each
watershed;
Identify areas where public safety is compromised and property
damage occurs due to stormwater runoff; and
identify funding sources that might be available to construct the
recommended drainage improvements identified by the Basin
Master Plan.
North Fork Catfish Creek Basin Plan
Several problem areas were identified within the North Fork Catfish Creek
drainage system. Figures 3-14, 3-15, and 3-16 in the Drainage Basin Master
Plan outline the flooding extents under existing and proposed conditions. The
benefit of the recommended improvements (alternative 2) is reflected by the
proposed conditions. Outlined in Table 1 is the $2,135,300 worth of
improvements recommended, and the order in which they should be constructed.
2
Figure 1. Bee Branch and North Fork drainage basins within the City of Dubuque (corporate limits
Bee Branch Basin Master Plan
The problems that exist in the Bee Branch basin became evident to the City on
May 16, 1999. Reports throughout the City indicated that between two and a half
(2.5) and five (5) inches of rainfall occurred in a five hour period.
The Drainage Basin Master Plan identifies over 1,150 homes and businesses in
the Bee Branch basin that are in the 100-year flood plain, at risk of flood damage
(see Figure 2).
Outlined in Table 2 are the recommended improvements within the W. 32nd
Street drainage basin, a sub-basin of the Bee Branch drainage basin. The
reduction in flooding depths that result from the W. 32nd Street improvements are
3
shown in Figure 3; 185 of the 1,155 homes and ousinesses are no longer at risk,
however, approximately 970 remain at risk.
Table 1. Recommended North Fork Catfish Creek Improvements, listed in the recommendec
order of construction.
I
Improvement
I Description Est. Cost
NW Arterial Detention Basin Excavate basin to increase the storage 56%
modifications to 81 Acre-feet $587,300~
Penn/JFK Culvert
improvembnts Build concrete structural headwall $165,000
Channel modifications from Increase channel to 25-foot bottom width with
Keyway to 530 feet east 3(H):I(V) side slopes $210,000
Keyway culvert modification Remove existing culverts and construct 3-
10'x8' Reinforced concrete boxes $332,000
Increase channel to 25-foot bottom width from
Channel modifications from Keyway to Ellen and 10-foot from Ellen to
Keyway to Rosemont Rosemont with 3(H): I(V) side slopes the $627,000
entire length
Rosemont culvert modification Build an additional 6-foot culvert $81,000
Channel modifications from Increase channel to 10-foot bottom width with
Rosemont to the NW Artedal 3(H):I(V) side slopes $133,000
TOTAL $2,135,300
Funding for the modifications to the NW Arterial Detention Basin was approved by City
Council in a previous year's Capital Improvement Project (CIP) budget. The basin will be
fully functional uy March of 2002.
it would require five times the size of the existing storm sewer to eliminate the
risk to the remaining 970 homes and businesses. Commonly referred to as the
Bee Branch storm sewer, the existing storm sewer is 20 feet wide by 12 feet high
at its largest point. The cost of building five such storm sewers exceeds $93
million.
Table 2. Recommended W 32"d Street sub-basin improvements.
improvement Description Est.
Cost
Upper Carter Detention Build an earthen berm. to create 182 acre-feet of
Basin storage. $875,000
W.32"d Street Detention Purchase 15 homes surrounding the existing basin
Basin and excavate within the basin to increase the $4,023,000
available storage 100% to 94 acre-feet.
TOTAL $4,898,000
4
Fi?ure 2. 100-~/ear floodin~ depths under existin~ conditions.
Altematively, it was discovered that an open channel originating at 24th and Elm
Streets and extending to the 16th Street detention cell would eliminate the dsk of
flood damage to the remaining 970 homes and businesses. Therefore, the
Drainage Basin Master Plan recommends the construction of the open channel.
The cost of the channel, which includes the purchasing of approximately 70
homes/businesses, is estimated at $17.1 million. Figure 4 shows the channel
extents.
5
Figure 3 Proiected flooding depths with W 32® Street sub basin improvements
--'TT ...... /' ........ T-
Historically, the Bee Branch Creek meandered through the North End. Over the
years the creek was lined by limestone, eventually covered, and transformed into
the Bee Branch storm sewer that exists today. The proposed channel is in reality
the restoration of the Bee Branch Creek.
With a 76-foot bottom width, the channel would be designed with mildly sloping
landscaped banks. It is anticipated that a 150-foot green corridor would be
required for the channel. The exact alignment of the channel is yet to be
determined. Depending on the alignment, between 60 and 80 homes/businesses
could be impacted.
6
Figure 4. Extents of the recommended flood control channel.
The recommended flood control channel would star~ at the 1~ Street detention cell (1) and
terminate at 24th and Elm Streets (2).
In summary, the Drainage Basin Master Plan recommends $24.1 million in
construction projects. Once the recommended improvements are constructed,
over 1,200 homes and businesses will no longer be at risk of flood damage from
heavy rainfall events.
Table 3. Drainage Basin Master Plan recommended in ~rovements.
Description
I Estimated Cost
North Fork Catfish Creek Basin improvements $2,135,300
W.32"~ Street Sub-Basin improvements $4,898,000
Bee Branch Creek Restoration $17,100,000
TOTAL $24,t33,300
Channel Corridor Study
For the purpose of estimating the cost of building a channel from 24th Street and
Elm to the 16th Street detention cell, a preliminary alignment was arbitrarily sited.
That alignment would require the purchasing of approximately 65 homes and 6
businesses. The estimate includes $7.1 million to purchase these properties.
At numerous public forums, City staff has informed citizens that the exact
alignment of the channel has not been determined. As can be expected, the
uncertainty of the channel location has caused considerable anxiety in the North
End neighborhoods.
A corridor study would establish the homes and businesses that the City might
buy to clear the way for the construction of the flood control channel. The
process of purchasing the necessary properties could proceed more
economically if negotiations can be minimized. This can be accomplished if the
City can purchase the proper~y on the open market, subject to an appraisal.
RECOMMENDATION
I recommend that the City Council adopt the attached resolution which has the
following effect:
1)
2)
Adopting the City of Dubuque Drainage Basin Master Plan as prepared
by HDR Engineering, Inc.; and
Authorizing the preparation of a Request for Prcoosats (RFP) for a
consulting engineering firm for the purpose of establishing the
alignment of the Bee Branch drainage channel described in the
Drainage Basin Master Plan.
BUDGET IMPACT
The costs associated with hiring a consulting firm for the channel corridor study
and a separate consulting firm to establish the stormwater utility will be presented
in the FY 2003 ClP budget.
ACTION TO BE TAKEN
The City Council is requested to adopt the attached resolution that:
1)
2)
Adopts the City of Dubuque Drainage Basin Master Plan; and
Authorizes the preparation of a Request for Proposals (RFP) to for a
consulting engineering firm for the purpose of establishing the
alignment of the Bee Branch drainage channel described in the
Drainage Basin Master Plan.
8
Prepared by Deron Muehring, Civil Engineer
Cc: Barry Lindahl, Corporation Council
Cindy Steinhauser, Assistant City Engineer
Pau line Joyce, Administrative Services Manager
Ken Tekippe, Finance Director
Mike Koch, Public Works Director
9
Prepared by: Michael A. Koch, Public Works Director Address: 50 W. 13th Street, Dubuque, IA 52001-4864
RESOLUTION NO.. 549-01
RESOLUTION ADOPTING THE CITY OF DUBUQUE DRAINAGE BASIN
MASTER PLAN AND AUTHORIZING A REQUEST FOR PROPOSALS FOR A
CORRIDOR STUDY TO ESTABLISH THE ALIGNMENT OF THE FLOOD CONTROL
CHANNEL RECOMMENDED IN THE DRAINAGE BASIN MASTER PLAN
Now, therefore, be it resolved by the City Council of the City of Dubuque, Iowa, is
as follows:
Whereas, the City Council of the City of Dubuque is committed to developing a
City-wide stormwater management master plan; and
Whereas, the 'City of Dubuque retained the firm of HDR Engineering, Inc. to
produce a drainage basin master plan; and
Whereas, the Drainage Basin Master Plan addresses flooding problems and
issues in the City of Dubuque and recommends certain public improvements to
implement the plan.
NOW THEREFORE, BE IT RESOLVED BY THE CITY COUNCIL OF THE CITY
OF DUBUQUE, IOWA:
Section 1. That the City of Dubuque Drainage Basin Master Plan prepared by
HDR Engineering, Inc., is hereby adopted.
Section 2. That the City Manager is authorized to issue a Request for
Proposals for a consulting engineering firm for the purpose of establishing the alignment
of the drainage channel in the Bee Branch basin as described in the Drainage Basin
Master Plan.
Passed, approved and adopted this 17th
Terrance M. Duggan, Mayor
Attest:
Jeanne F.. Schneider, City Clerk
dayof December, 2001.
MEMORANDUM
December14.2001
TO:
FROM:
SUBJECT:
The Honorable Mayor and City Council Members
Michael C. Van Milligen, City Manager
Stormwater Management Plan
Attached is additional information for Agenda Action Item #7 regarding the Stormwater
Management Plan.
MCVM/jh
Attachment
CC:
Michael C. Van Milligen
Barry Lindahl, Corporation Counsel
Cindy Steinhauser, Assistant City Manager
Laura Carstens, Planning Services Manager
David Harris, Housing and Community Development Director
Gus Psihoyos, Assistant City Engineer
Deron Muehring, Civil Engineer
..I
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I
~.1
City of Dubuque, Iowa
Drainage Basin Master Plan
Fall 2001
I-DR
HDR Engineering, Inc.
8404 Indian Hills Drive
Omaha, NE 68114
TABLE OF CONTENTS
Section Paqe No.
EXECUTIVE SUMMARY ....................................................................................................... E-1
1.0
2.0
INTRODUCTION .......................................................................................................... 1-1
1.1 PROJECT BACKGROUND ................................................................................... 1-1
1.2 PROJECT OBJECTIVES ........................................................................................ 1-2
1.3 ORGANIZATION OF THE DRAINAGE BASIN MASTER PLAN ..................... 1-3
1.4 NATIONAL POLLUTANT DISCHARGE ELIMINATION SYSTEM ................ 1-4
METHODOLOGIES ..................................................................................................... 2-1
2.1 PHYSICAL CHARACTERISTICS ........................................................................ 2-1
2.1.1 Topography .................................................................................................. 2-1
2.1.2 Soil Types ..................................................................................................... 2-2
2.2 URBAN DEVELOPMENT CHARACTERISTIC S ............................................... 2-2
2.2.1 Land Use ...................................................................................................... 2-2
2.3 HYDROLOGIC MODEL ........................................................................................ 2-3
2.3.1 Model Schematic .......................................................................................... 2-4
2.3.2 NRCS Runoff Curve Number ....................................................................... 2-5
2.3.3 NRCS Unit Hydrograph ............................................................................... 2-6
2.3.4 Rainfall ......................................................................................................... 2-7
2.3.5 Channel Routing ........................................................................................ 2-10
2.3.6 Reservoir Routing ...................................................................................... 2-10
2.3.7 CRWR-PrePro ........................................................................................... 2-11
2.4 HYDRAULIC MODELS ...................................................................................... 2-13
2.4.1 Model Schematic ........................................................................................ 2-14
2.4.2 Model Calibration ...................................................................................... 2-14
2.4.3 Channel and Structure Improvements ....................................................... 2-14
2.4.4 Drainage Criteria ...................................................................................... 2-15
2.4.5 Cost Estimates ............................................................................................ 2-15
2.5 WATER QUALITY .............................................................................................. 2-15
2.5.1 Operational BMPs ..................................................................................... 2-16
2.5.2 Structural BMPs ........................................................................................ 2-18
2.6 DEVELOPMENT OF RECOMMENDED PLAN ................................................ 2-20
2.6.1 General ...................................................................................................... 2-20
2.6.2 Structural Flooding .................................................................................... 2-20
2.6.3 Roadway Overtopping ............................................................................... 2-20
2.6.4 Flood Minimization Alternative Improvements ......................................... 2-21
City of Dubuque, Iowa Drainage Basin Master Plan
Table of Contents i Fall 2001
TABLE OF CONTENTS
Section
Paqe No.
3.0
4.0
NORTH FORK CATFISH CREEK DRAINAGE BASIN ......................................... 3-1
3.1 GENERAL DRAINAGE BASIN DESCRIPTION .................................................3-1
3.2 FLOOD HYDROLOGY .......................................................................................... 3-3
3.3 STREAM HYDRAULICS ........................................ i ............................................. 3-5
3.4 PROBLEM AREAS ................................................................................................ 3-7
3.5 DEVELOPMENT OF ALTERNATIVE SOLUTIONS .......................................... 3-9
3.5.1 Detention ...................................................................................................... 3-9
3.5.2 Channel and Drainage Structure Improvements ....................................... 3-12
3.5.3 Flood lnundation ....................................................................................... 3-16
3.6 RECOMlVIENDATIONS FOR IMPROVEMENT ALTERNATIVES ................. 3-16
3.7 PROJECT PHASING ............................................................................................ 3-18
BEE BRANCH DRAINAGE BASIN ........................................................................ ....4-1
4.1 GENERAL DRAINAGE BASIN DESCRIPTION .................................................4-1
4.2 WEST 32ND STR~T DRAINAGE SUBAREA ...................................................4-5
4.2.1 General Subarea Description ...................................................................... 4-5
4.2.2 Flood Hydrology .......................................................................................... 4-6
4.2.3 Stream Hydraulics ....................................................................................... 4-7
4.2.4 Problem Areas ............................................................................................. 4-9
4.2.5 Development of Alternative Solutions ........................................................ 4-10
4.2.6 Recommendations for lmprovement Alternatives ...................................... 4-16
4.2.7 Project Phasing .......................................................................................... 4-16
4.3 KAUFMANN AVENUE DRAINAGE SUBAREA ............................................. 4-17
4.3.1 General Subarea Description .................................................................... 4-17
4.3.2 Flood Hydrology ........................................................................................ 4-18
4.3.3 Stream Hydraulics ..................................................................................... 4-19
4.3.4 ProblemAreas ........................................................................................... 4-19
4.3.5 Development of Alternative Solutions ........................................................ 4-21
4.3.6 Recommendations for lmprovement Alternatives ...................................... 4-22
4.3.7 Project Phasing .......................................................................................... 4-22
4.4 LOCUST STREET DRAINAGE SUBAREA ....................................................... 4-23
4.4.1 General Subarea Description .................................................................... 4-23
4.4.2 Flood Hydrology ........................................................................................ 4-23
4.4.3 Stream Hydraulics ..................................................................................... 4-24
4.4.4 Problem Areas ........................................................................................... 4-25
4.4.5 Development of Alternative Solutions ........................................................ 4-27
4.4.6 Recommendations for lmprovement Alternatives ...................................... 4-28
City of Dubuque, Iowa Drainage Basin Master Plan
Table of Contents ii Fall 2001
TABLE OF CONTENTS
Section Paqe No.
4.4.7 Project Phasing .......................................................................................... 4-28
4.5 CENTRAL BUSINESS DISTRICT - NORTH SUBAREAS .............................. 4-28
4.5.1 General Subarea Description .................................................................... 4-28
4.5.2 Flood Hydrology ........................................................................................ 4-29
4.5.3 Stream Hydraulics ..................................................................................... 4-30
4.5.4 Problem Areas ........................................................................................... 4-37
4.5.5 Development of Alternative Solutions ........................................................ 4-39
4.5.6 Recommendations for lmprovement Alternatives ......................................4-40
4.5.7 Project Phasing .......................................................................................... 4-40
4.6 CENTRAL BUSINESS DISTRICT SUBAREAS ................................................ 4-40
4.6. I General Subarea Description .................................................................... 4-40
4.6.2 Flood Hydrology ........................................................................................ 4-4]
4.6.3 Stream Hydraulics ..................................................................................... 4-42
4. 6.4 Problem Areas ........................................................................................... 4-42
4.6.5 Development of Alternative Solutions ........................................................ 4-42
4.6.6 Recommendations for lmprovement Alternatives ......................................4-43
4.6.7 Project Phasing .......................................................................................... 4-43
4.7 BEE BRANCH STORM SEWER TRUNK LINE ................................................ 4-43
4.7. I Development of Alternative Solutions ........................................................ 4-45
4.7.2 Recommendations for lmprovement Alternatives ......................................4-47
4. 7.3 Project Phasing .......................................................................................... 4-54
5.0 FINANCING DRAINAGE IMPROVEMENTS AND OPERATIONS .................... 5-1
5.1 GENERAL FUND FINANCING ............................................................................ 5-1
5.2 FUNDING OPERATION AND MAINTENANCE ACTIVITIES ......................... 5-2
5.3 CAPITAL FUNDING ........... ~ .................................................................................. 5-2
5.3.1 Pay-As-You-Go ......... ~ .................................................................................. 5-2
5.3.2 General Obligation Bonds ........................................................................... 5-3
5.3.3 Revenue Bonds ............................................................................................. 5-3
5.3.4 Grants .......................................................................................................... 5-4
5.3.5 Developer Contributions .............................................................................. 5-5
5.4 CAP1TAL RECOVERY .......................................................................................... 5-5
5.4.1 Monthly User Charges ................................................................................. 5-5
5.4.2 Impact Fees .................................................................................................. 5-5
5.5 MUNICH>AL DRAINAGE UTI]~ITIES .................................................................5-6
BIBLIOGRAPHY ..................................................................................................................... B-1
City of Dubuque, Iowa Drainage Basin Master Plan
Table of Contents iii Fall 200]
TABLE OF CONTENTS
LZST OF TABLES
Table Paqe No.
Table 1.1
Table 2.1
Table 2.2
Table 2.3
Table 2.4
Table 2.5
Table 2.5
Table 2.6
Table 2.7
Table 2.8
Table 3.1
Table 3.2
Table 3.3
Table 3.4
Table 3.5
Table 3.6
Table 3.7
Table 3.8
Table 3.9
Table 3.10
Table 4.1
Table 4.2
Table 4.3
Table 4.4
Table 4.5
Summary of Maximum 24-Hour Rainfall Events for Dubuque, Iowa ................. 1-2
Drainage Basin Land Use Groups ................................................. t ...................... 2-3
Drainage Area Land Use Groups and Curve Number .................../[ ...................... 2-5
C~ty of Dubuque 24-Hour Total Rainfall Depths .......................... ~ ...................... 2-7
North Fork Catfish Creek Peak 100-Year Discharge Comparison
at Confluence with Middle Fork Catfish Creek ................................................... 2-8
City of Dubuque 15-Minute Time Distribution for 24-Hour Ston a Event .......... 2-9
City of Dubuque 15-Minute Time Distribution for 24-Hour Ston a Event ........ 2-10
Spatial Data for CRWR-PrePro ......................................................................... 2-12
Roadway Overtopping Design Storms .............................................................. 2-21
Flood Minimization Alternative Improvements ................................................ 2-22
North Fork Catfish Creek Drainage Basin Soil Type Summary ......................... 3-2
North Fork Catfish Creek Drainage Basin Land Use Summary ...l ...................... 3-3
North Fork Catfish Creek Drainage Basin Peak Runoff Summar~ for
Existing Drainage System Conditions .......................................... l ...................... 3-4
North Fork Catfish Creek Drainage Basin Existing Hydraulic C~ pacity
of Stream Crossings Summary ............................................................................. 3-5
North Fork Catfish Creek Drainage Basin Existing Hydraulic Ca ?acity
and Return Period of Stream Crossings Summary ............................................... 3-6
North Fork Catfish Creek Drainage Basin Identified Problem Ar ~a Summary... 3-8
North Fork Catfish Creek Drainage Basin Detention Storage Sur unary ......... ,3-11
North Fork Catfish Creek Drainage Basin Main Channel and Sty tctural
Improvement Summary ..................................................................................... 3-14
North Fork Catfish Creek Drainage Basin Peak Runoff Summar, for
Existing and Proposed Hydraulic Conditions .............................. .[ .................... 3 - 16
North Fork Catfish Creek Drainage Basin Recommended Impro?ements
Summary ...................................................................................... 1.[ .................... 3-18
Bee Branch Drainage Basin Drainage Areas for Subareas .......... 't ...................... 4-2
Bee Branch Drainage Basin Soil Type Summary ................................................
Bee Branch Drainage Basin Land Use Summary .........................
West 32nd Street Drainage Subarea Peak Runoff Summary Exisl
System Conditions ........................................................................
West 32nd Street Drainage Subarea Existing Hydraulic Capacit
Crossings Summary .......................................................................
lng Drainage
...................... 4-6
of Stream
City of Dubuque, Iowa Drainc 'e Basin Master Plan
Table of Contents iv Fall 2001
TABLE OF CONTENTS
Table
Table 4.6
Table 4.7
Table 4.8
Table 4.9
Table 4.10
Table 4.1 t
Table 4.12
Table 4.13
Table 4.14
Table 4.15
Table 4.16
Table 4.17
Table 4.18
Table 4.19
Table 4.20
Table 4.21
Table 4.22
Table 4.23
Table 4.24
Table 4.25
Lin' OF TABLES
Paqe No.
West 32nd Street Drainage Subarea Existing Hydraulic Capacity and
Return Period of Stream Crossings Summary ...................................................... 4-8
West 32nd Street Drainage Subarea Identified Problem Area Summary ............ 4-9
West 32nd Street Drainage Subarea Detention Sites Investigated ..................... 4-11
West 32nd Street Subarea Detention Improvement Alternative Summary ........ 4-13
West 32nd Street Subarea Detention Storage and Discharge Summary ............ 4-14
West 32nd Street Subarea Detention Improvement Alternative and Estimated
Construction Cost Summary .............................................................................. 4-15
West 32nd Street Drainage Subarea Recommended Improvements
Summary ............................................................................................................ 4-17
Kanfmann Avenue Drainage Subarea Peak Runoff Summary Existing
Drainage System Conditions .............................................................................. 4-18
Kaufmann Avenue Drainage Subarea Existing Hydraulic Capacity
Summary ............................................................................................................ 4-20
Kaufmann Avenue Drainage Subarea Recommended Improvements
Summary ............................................................................................................ 4-22
Locust Street Drainage Subarea Peak Runoff Summary Existing Drainage
System Conditions ............................................................................................. 4-23
Locust Street Drainage Subarea Existing Hydraulic Capacity Summary .......... 4-26
Locust Street Drainage Subarea Hydraulic Capacity for Storm Sewer
Replacement ....................................................................................................... 4-27
Central Business District - North Drainage Subareas Peak Runoff Summary
for Existing Drainage System Conditions .......................................................... 4-30
Washington Street Drainage Subarea Peak Runoff Summary Existing
Drainage System Conditions Along Bee Branch Trunk line ............................. 4-31
Central Business District - North Drainage Subareas Existing Hydraulic
Capacity Summary ............................................................................................. 4-36
Central Business District - North Drainage Subareas Existing Hydraulic
Capacity Summary ............................................................................................. 4-38
Central Business District - North Drainage Subareas Hydraulic Capacity
for Storm Sewer Replacement ............................................................................ 4-39
Central Business District - North Drainage Subareas Detention Storage
Summary ............................................................................................................ 4-40
Central Business District Drainage Subareas Peak Runoff Summary
Existing Drainage System Conditions ............................................................... 4-41
City of Dubuque, Iowa Drainage Basin Master Plan
Table of Contents v Fall 2001
TABLE OF CONTENTS
Table.
Table 4.26
Table 4.27
Table 4.28
Table 4.29
Table 5.1
Table 5.2
LIST OF TABLES
Paqe No.
Central Business District Drainage Subareas Existing Hydraulic Capacity
Summary ............................................................................................................ 4-44
Bee Branch Drainage Basin Flood Minimization Altemative Improvements ...445
Bee Branch Drainage Basin Downstream Boundary Conditions for Relief
Sewer Alternative ............................................................................................... 4-50
Bee Branch Drainage Basin Downstream Boundary Conditions for
Flood Control Channel Alternative .................................................................... 4-52
Municipal Drainage Utilities in Iowa ................................................................... 5-7
Estimated Annual Revenue for the City of Dubuque With Implementation
of Municipal Drainage Utility with Comparable Fee Structures ......................... 5-8
Fiqure
Figure 1-1
Figure 3-1
Figure 3-2
Figure 3-3
Figure 34
Figure 3-5
Figure 3-6
Figure 3-7
Figure 3-8
Figure 3-9
Figure 3-10
Figure 3-11
Figure 3-12
Figure 3-13
Figure 3-14
LIST OF FIGURES
Drainage Basins Studied
North Fork Catfish Creek Drainage Basin General Drainage Basin
North Fork Catfish Creek Drainage Basin Basin Slope Map
North Fork Catfish Creek Drainage Basin Soil Classification Map
North Fork Catfish Creek Drainage Basin Land Use Classification
North Fork Catfish Creek Drainage Basin HEC-HMS Subbasin Delineation
North Fork Catfish Creek Drainage Basin HEC-HMS Model Schematic
North Fork Catfish Creek Drainage Basin Identified Problem Areas
North Fork Catfish Creek Drainage Basin Detailed Detention Alternative at
Northwest Arterial
North Fork Catfish Creek Drainage Basin Detailed Detention Alternative at
Pennsylvania Ave.
North Fork Catfish Creek Drainage Basin Reach: Northwest Arterial to Rosemont
North Fork Catfish Creek Drainage Basin Reach: Rosemont to Pennsylvania
North Fork Catfish Creek Drainage Basin Reach: Pennsylvania to University
North Fork Catfish Creek Drainage Basin Proposed Inlet Improvements at
Pennsylvania
North Fork Catfish Creek Drainage Basin Flood Inundation Map - Rosemont to
Winnie
City of Dubuque, Iowa Drainage Basin Master Plan
Table of Contents vi Fall 2001
TABLE OF CONTENTS
Fiqure
Figure 3-15
Figure 3-16
Figure 3-17
Figure 4-1
Figure 4-2
Figure 4-3
Figure 4-4
Figure 4-5
Figure 4-6
Figure 4-7
Figure 4-8
Figure 4-9
Figure 4-10
Figure 4-11
Figure 4-12
Figure 4-13
Figure 4-14
Figure 4-15
Figure 4-16
Figure 4-17
Figure 4-18A
Figure 4-18B
Figure 4-19
Figure 4-20
Figure 4-21
Figure 4-22
ErST OF FIGURES (CON'I~D)
North Fork Catfish Creek Drainage Basin Flood Inundation Map - Winnie to
Carter
North Fork Catfish Creek Drainage Basin Flood Inundation Map - Carter to Ideal
North Fork Catfish Creek Drainage Basin Flood Inundation Map - Ideal to
University
Bee Branch Drainage Basin Drainage Basin Subareas
Bee Branch Drainage Basin Basin Slope Map
Bee Branch Drainage Basin Soil Classification Map
Bee Branch Drainage Basin Land Use Classification
Washington Street Drainage Subarea Existing 100-year Flood Inundation -
Lower Reach
West 32nd Street Drainage Subarea HEC-HMS Subbasin Delineation
West 32nd Street Drainage Subarea HEC-HMS Model Schematic
West 32nd Street Drainage Subarea Detention Sites Investigated
West 32nd Street Drainage Subarea Detention Site Alternatives
West 32nd Street Drainage Subarea - West 32nd Street Detention Basin
Improvements
Kanfmann Avenue Drainage Subarea HEC-HMS Subbasin Delineation
Kaufmann Avenue Drainage Subarea HEC-HMS Model Schematic
Kaufmann Avenue Drainage Subarea Detention Site Alternative
Locust Street Drainage Subarea HEC-HMS Subbasin Delineation
Locust Street Drainage Subarea HEC-HMS Model Schematic
Central Business District - North Drainage Subareas HEC-HMS Subbasin
Delineation
Central Business District - North Drainage Subareas HEC-HMS Model Schematic
Washington Street Drainage Subarea Bee Branch Storm Sewer Trunk Line XP-
SWMM Model Schematic (1 of 2)
Washington Street Drainage Subarea Bee Branch Storm Sewer Trunk Line XP-
SWMM Model Schematic (2 of 2)
Central Business District Drainage Subareas HEC-HMS Subbasin Delineation
Central Business District Drainage Subareas HEC-HMS Model Schematic
Bee Branch Drainage Basin Identified Problem Areas
Washington Street Drainage Subarea West 32nd Street Improvement Impacts
City of Dubuque, Iowa Drainage Basin Master Plan
Table of Contents vii Fall 2001
TABLE OF CONTENTS
LIST OF FIGURES (CONT'D)
Fiqure
Figure 4-23
Figure 4-24
Figure 4-25
Figure 4-26
Bee Branch Drainage Basin Proposed Relief Sewer Alternative
Bee Branch Drainage Basin Proposed Flood Control Channel Alternatives
Washington Street Drainage Subarea Phase I Flood Control Channel Impacts
Washington Street Drainage Subarea Phase I and II Flood Control Channel
Impacts
TECHNICAL APPENDICES
Opinion of Probable Construction Costs Appendix
Hydrologic and Hydraulic Appendices (Under Separate Cover)
City of Dubuque, Iowa Drainage Basin Master Plan
Table of Contents viii Fall 2001
EXECUTIVE SUMMARY
The primary objectives of this Drainage Basin Master Plan are to address the issue of storm
water conveyance in major streams, identify existing and future problem areas, and develop
recommendations for solutions to specific problem areas. The North Fork Catfish Creek and Bee
Branch Drainage Basins were the only two drainage basins analyzed with the described goals.
Specifically, the objectives of this Master Plan include:
· Determining capacity of existing drainage system under ultimate development
conditions for the 10-, 50-, 100- and 500-year return period storm events;
· Developing hydraulic models using aerial topographic mapping and GIS information
for major drainage segments on North Fork Catfish Creek and the Bee Branch main
trunk hne storm sewer;
· Identifying problem areas in the stream segments studies and developing
improvement plans for specific problem areas;
· Addressing water quality in a qualitative nature by developing a list of possible Best
Management Practices (BMPs); and
· Identifying potential funding sources for improvement plans.
A total of nine (9) problem areas located within the North Fork Catfish Creek Drainage Basin
were identified as out of compliance with the City's drainage standards/criteria. The majority of
these problem areas are associated with limited hydraulic capacity of existing detention cells,
natural channels, and culverts. The total cost for implementation of recommended improvements
in the North Fork Catfish Creek Drainage Basin is estimated to be $1,673,000.
The Bee Branch Drainage Basin is composed of five (5) major subareas: West 32nd Street,
Kaufmann Avenue, Locust Street, Central Business District - North, and Central Business
District. Most of the specific problem areas identified in the Bee Branch Drainage Basin were
located within the West 32nd Street Subarea. Seven (7) problem areas in the West 32nd Street
Subarea, including one special problem area, exceeded the established design criteria. Most of
the flooding problem areas are the result of limited hydraulic capacity of drainage structures.
The West 32nd Street Subarea also was identified as a primary factor in the flooding hazards
encountered in the low-lying, heavily developed area located in the lower portion of the Bee
Branch Drainage Basin, also known as the Couler Valley area. The West 32nd Street Subarea
was recognized as offering the best opportunity for storm water storage within the Bee Branch
Drainage Basin; therefore, the recommended improvements focused on providing additional
storage for storm water runoff. The total estimated capital cost for execution of the
recommended improvements in the West 32nd Street Subarea is approximately $4,700,000. An
itemized list of improvements can be found in Table 4.12 on page 4-19.
City of Dubuque, Iowa Drainage Basin Master Plan
Executive Summary E-1 Fall 2001
EXECUTI'VE SUMMARY
The primary drainage problems within the Kaufmann Avenue, Locust Street, Central Business
District - North, and Central Business District Subareas have occurred where development has
exceeded the capacity of the storm water conveyance system. The only viable detention storage
option for these subareas was a small detention cell in the Kaufmann Avenue Subarea. The
estimated capital cost for this detention cell is approximately $530,000.
Flooding problems in the upper portion of the main Bee Branch storm sewer trunk line, north of
24th Street, are greatly improved with the West 32nd Street Subarea improvements; however, the
convergence of flood flows from Kaufmann, Locust, and Central Business District - North
Subareas still result in significant flooding depths in the lower part of the drainage area south of
24th Street. The only alternative that significantly reduced 100-year flooding depths in the lower
reaches of the Bee Branch was a flood control channel. This alternative consists of constructing
a 150-foot wide, flood control channel to carry the flow of a 100-year flood event. Construction
of this channel from the 16th Street Detention Cell to 24th Street was shown to remove
approximately 99% of the homes and businesses from the 100-year floodplain along the main
Bee Branch storm sewer trunk line, while requiring the purchasing or relocation of
approximately 70 homes and/or businesses. Estimated cost for this alternative is $1T1 million.
Ciiy of Dubuque, Iowa Drainage Basin Master Plan
Executive Summary E-2 Fall 2001
INTRODUCTZON
1.0 I'NTRODUCTi'ON
1.1 PRO3ECT BACKGROUND
The City of Dubuque (City) is located in the eastern portion of Dubuque County in eastern Iowa.
The corporate limits of the City cover approximately 25 square miles and include a population of
approximately 57,000 people. The City is located on the west or right bank of the Mississippi
River and is characterized by numerous outcrops of limestone and steep slopes in the upland
areas and generally flat low-lying floodplains in the lowlands. Earthen levees and floodwalls
offer protection to the city against a Mississippi River flood. Along the river, numerous
temporary storage sites are filled with storm water during a storm event and discharge into the
Mississippi River through ~:avity outlets or pump stations when gravity drainage is not possible.
The streams and channels existing in the City of Dubuque predominately originate within the
corporate limits and flow easterly to the Mississippi River. The City is principally drained by the
Bee Branch Drainage Basin (Bee Branch), North Fork Catfish Creek Drainage Basin (North
Fork), and their tributaries. The Bee Branch flows through the north end of the city and consists
of several large tributary drainage areas including West 32nd Street, Kaufmann Avenue, Locust
Street, Central Business District - North, and Central Business District. The low-lying, heavily
developed areas located in the Central Business District - North and Central Business District
are hereafter referred to as the Couler Valley area, while the North Fork Catfish Creek Drainage
Basin consists primarily of one main channel with several small tributary drainage areas. The
Bee Branch Drainage Basin flows into the 16th Street Detention Cell adjacent to the Mississippi
River, and the North Fork Catfish Creek Drainage Basin empties into Middle Fork Catfish
Creek. The Bee Branch and North Fork Catfish Creek Drainage Basins drain a total of 11.0
square miles and were identified by the City of Dubuque as the focus of the study. The
contributing drainage areas of the Bee Branch and North Fork are shown in Figure 1-1.
Flooding periodically occurs along the streams and streets in Dubuque, with flood damage to
streets, homes and businesses. As the city enjoys sustained growth through the years, runoff
rates and flooding problems are likely to increase in many areas due to continued conversion of
rural lands to urban uses.
A review of the rainfall records for the City of Dubuque shows that storms exceeding the
magnitude of a 50-year and 100-year return period have occurred in the past and will likely
continue to occur in the future. Daily rainfall has been recorded at the Dubuque Airport since
1896 and at Check Dam 11 located on the Mississippi River since 1937. Table 1.1 presents a
summary of the ten greatest 24-hour rainfall measurements at the two (2) stations. It is noted
City of Dubuque, Iowa Drainage Basin Master Plan
Introduction 1- I Fall 2001
INTRODUCTION
that the maximum 24-hour rainfall events may not be taken within the same 24-hour period for
each of the rainfall stations, such as the September 14, 1967 storm event.
Table 1.1
Summary of Maximum 24-Hour Rainfall Events for Dubuque, Iowa
1 Septem~r 14, 1967 8.85 Au~st 2, 1972 5.27
2 J~y 1, 1961 6.28 May 13, 1978 4.50
3 November 2, 1961 4.79 September 13, 1972 4.48
4 May 6, 1960 4.37 September 14, 1967 4.04
5 September 12, 1961 4.37 J~e 13, 1947 3.88
6 JOy 8, 1951 4.36 J~y 30, 1987 3.86
7 August 16, 1918 4.26 [ May 29, 1962 3.64
8 I~y 17, 1977 3.91 August 7, 1970 3.40
9 J~y 5, 1993 3.91 = August 27, 1965 3.35
10 J~e 13, 20~ 3.84 J~e 26, 1969 3.33
Urban development within a drainage area generally results in an increase in the percent
impervious, i.e., more hard surfaces, with a concurrent increase in runoff associated with any
given storm event. Therefore, stream channels and coverts that were adequate prior to
urbanization may become inadequate as the drainage area develops. This results in more
frequent stream channel flooding and backwater flooding from culverts unable to convey the
higher discharges. The City of Dubuque addresses these problems, as funds allow, through street
and drainage improvement projects.
Z.2 PROJECT OBJECTIVES
This Drainage Basin Master Plan addresses the issue of storm water conveyance in major
streams, the identification of existing and future problem areas that do not meet drainage criteria
and the development of recommendations for solutions to specific problem areas. The primary
objectives of this Drainage Basin Master Plan are the following:
1. Determine capacity of existing drainage system under ultimate development
conditions for the 10-, 50-, 100- and 500-year return period storm events;
City of Dubuque, Iowa Drainage Basin Master Plan
Introduction 1-2 Fall 2001
TNTRODUCTZON
2. Develop hydraulic models using aerial topographic mapping and GIS information
for major drainage segments on North Fork Catfish Creek and the Bee Branch main
trunk line storm sewer;
3. Identify problem areas in the stream segments studies and develop improvement
plans for specific problem areas;
4. Address water quality in a qualitative nature by developing a list of possible Best
Management Practices (BMPs); and
5. Identify potential funding sources for improvement plans.
This Drainage Basin Master Plan addresses existing and projected flooding within the drainage
areas. Portions of the drainage areas have been included in previous Federal Emergency
Management Agency (FEMA) studies. While FEMA flood insurance studies are the official
regulatory document for floodplain identification within Dubuque, they are lacking in three (3)
areas: 1) they are based on very coarse hydrologic information, 2) they do not include drainage
areas smaller than 1 square mile, and 3) they do not consider the impacts of ultimate
development patterns. The Master Plan addresses these deficiencies by using more detailed
hydrologic techniques. While not regulatory, the floodplains delineated in this Drainage Basin
Master Plan are a more accurate representation of expected floodplains for planning purposes.
Lastly, the floodplain delineation noted above includes considerations of ultimate development
patterns.
Specifically, this Master Plan identifies the anticipated future hydrology (rainfall and mnof0 for
the drainage area considering reasonable land use changes based on ultimate development.
Problem areas were identified for the existing system without any improvements at the future
flows. Alternatives were evaluated and solutions recommended based on ultimate flows.
This Master Plan addresses water quality in a qualitative nature within the drainage areas. The
levels of pollutants typically associated with urban runoff were not calculated. Although it was
not directly addressed in this plan, implementation of best management practices (BMPs) and
impacts on water quality were considered in the analysis of alternatives.
1.3 ORGANIZATION OF THE DRAINAGE BAS'tN MASTER PLAN
The Drainage Basin Master Plan is divided into five (5) main sections. Section 1 is the
introduction. Section 2 provides a description of the methodologies used in the performance of
this study including a description of the flood hydrology and stream hydraulic models, a
discussion of the drainage criteria applied, and a description of the methods for the development
of drainage cost improvement estimates. Sections 3 and 4 include the individual sub-section of
City of Dubuque, Iowa Drainage Basin Master Plan
Introduction 1-3 Fall 2001
TNTRODUCTION
each of the two (2) major drainage basins in Dubuque including North Fork Catfish Creek and
the Bee Branch Drainage Areas. The Bee Branch Drainage Area includes: West 32nd Street,
Kanfmann Avenue, Locust Street, Windsor Avenue, 8th Street, llth Street, 15th Street, Lower
and Upper Kerper and Dock Street and Hamilton Street Subareas. Each drainage basin sub-
section include a description of the general characteristics of the drainage area, flood hydrology
results, hydraulic capacity of roadway crossings, identification of problem areas, conceptual
improvement plans to mitigate flooding in the problem areas and capital cost estimates for each
improvement project. A ranking of the problem areas for each of the individual drainage basins
was prepared to establish priorities for implementation of proposed projects. Although
numerous criteria could be used to establish priorities for implementation of the proposed
projects, the following criteria (arranged in order of decreasing importance) were considered:
· Severity of existing problem;
· Public safety;
· Capital cost;
· Preserving/enhancing existing property values;
· Development potential;
· Social/economic impacts; and
· Maintenance/operating costs.
Flooding of residential, commercial and industrial buildings was given the highest priority for
implementation of improvement projects. Roadway crossings failing to meet the drainage criteria
were prioritized for improvement based on apparent traffic volumes, availability of alternate
routes that are passable during flood events, frequency and degree of overtopping, and cost
efficiency for mitigating the flooding problem. Section 5 addresses the financing of drainage
improvements and operations.
1.4 NATIONAL POLLUTANT DISCHARGE ELIMINATION SYSTEM
The 1987 Amendments to the Clean Water Act recognized urban runoff as a major contributor to
the Nation's water quality problem. Thereafter, storm water issues became as closely allied with
water quality issues as they had been previously associated with flood control. In other words,
quality became as important as quantity. In 1990, the U.S. Environmental Protection Agency
(EPA) promulgated Phase t of the National Pollutant Discharge Elimination System (NPDES)
permit coverage to address storm water runoff from "medium and large" municipal separate
storm sewer systems (MS4s). Storm Water Phase II program is the next phase of EPA's effort
to preserve, protect and improve the Nation's water resources from polluted storm water runoff.
City of Dubuque, lowa Drainage Basin Master Plan
Introduction 1-4 Fall 2001
INTRODUCTION
Dubuque meets the definition of a small (MS4) sized municipality (population more than 50,000
but less than 100,000). The deadline for submittal of permit applications for Phase II designated
small MS4s is March 10, 2003.
Six measures are to be included in a storm water management program to meet the conditions of
its NPDES permit and include: 1) public education and outreach; 2) public
participation/involvement; 3) illicit discharge detection and elimination; 4) construction site
runoff control; 5) post-construction storm water management in new development and
redevelopment and 6) municipal pollution prevention/good housekeeping. These measures
comprise the range of Best Management Practices (BMPs) available to a municipality for the
reduction of negative impacts resulting from storm water runoff. BMPs are defined as schedules
of activities, prohibitions of practices, maintenance procedures, and other physical, structural,
and/or managerial practices to prevent or reduce the pollution of waters of the United States.
City of Dubuque, lowa Drainage Basin Master Plan
Introduction 1-5 Fall 2001
Illinois
CITY BOUNDARY
HDR Engineering, Inc,
Source: Dubuque Area Gc=~graphic lnforma~on System (DAGIS), dated May 2000
Drainage Basins Studied
~)~ Drainage Basin Master Plan
,~,,~,//~.,~,~,,~. City of Dubuque, Iowa
FALL 2001
Figure
METHODOLOGIES
2.0 iVlETHODOLOGIES
Flood hydrology models were developed for each individual drainage basin, incorporating the
unique characteristics of each basin to simulate runoff for specific storm events. Stream
hydraulic models were developed for the segments included in this study incorporating the
channel and floodplain geometry derived from aerial topographic maps, roughness
characteristics of channel banks and floodplains and the numerous bridges and culverts that cross
the streams and affect flood levels. The following sections describe the methodologies used in
this study.
PHYSICAL CHARACTERISTICS
2.1.1 Topography
Topography of a drainage area refers to the characteristics and features of the land surface, such
as slope and channel width. The slope of a drainage area influences the rate at which
precipitation falling on the land surface will be conveyed to the outlet point of the drainage area.
All other parameters considered equal, as the slope of a drainage area increases, the faster the
water travels to the outlet point. Although there can be a great deal of variation in slope
magnitude and direction within a drainage area, there are two main slope values of particular
interest: 1) average overland slope and 2) average channel slope. Overland slope gives an
indication of how fast runoff will travel on the land surface to a drainage channel, and channel
slope relates how quickly the runoff will be routed to the outlet point of the drainage area.
B2'ainage areas within the City typically have a much steeper overland slope than channel slope.
Elevation measurements and slope calculations were performed using the Dubuque Area
Geographic Information System (DAGIS). The DAGIS included a digital terrain model (DTM)
consisting of spot elevations and breaklines generated from aerial survey and ground control
data. Two-foot elevation contour lines created fi.om the DTM were also included in the DAGIS
database. The DTM was used to produce two additional terrain models for use in the analysis.
A triangular irregular network (TIN) terrain model, a continuous surface comprised of triangular
faces, was created for use in calculating detention volumes, cutting stream cross-sections, and
creating open channel hydraulic models. A digital elevation model (DEM), a grid comprised of
10-meter cells, was created from the TIN for use in delineating drainage areas, estimating
hydrologic parameters, and creating hydrologic models.
City of Dubuque, Iowa Drainage Basin Master Plan
Methodologies 2-1 Fall 2001
METHODOLOGI'ES
2.1.2 Soil Types
The types of soils present in a drainage area have a significant impact on the amount of runoff a
given storm will produce. This impact is influenced primarily by the infiltration characteristics
of the soil.
Information on the soil types and characteristics for each drainage area was compiled by
developing a digital soils database in GIS. Soil survey SSURGO and SATSGO databases
developed by the Natural Resources Conservation Service (NRCS) were used. The SSURGO
data set was used to provide specific information about each soil series within the drainage areas.
Because the majority of the soils in the Dubuque area are classified as hydrologic soil group 'B,'
the less detailed STATSGO database was used to develop hydrologic models. This information
was then combined with land use data to obtain hydrologic characteristics for each polygon.
2.2 URBAN DEVELOPMENT CHARACTERISTICS
2.2.1 Land Use
Land use is a critical element for storm water planning. It impacts both the quantity and quality
of water being routed through storm sewer systems and natural channels. The effect land use has
on water quantity is generally linked to the amount of impervious area for a particular land use
category. The more impervious area a tract of land has, the faster the water will be routed to the
storm sewer system or channel due to lower infiltration losses into the ground and lower surface
roughness of the land. In general, an area with a high percentage of impervious area will have a
quicker time to peak and a higher peak, than a similar area with a lower percentage impervious.
The scope of this project was to model storm water quantity for ultimate development, so a land
use database containing information for ultimate development was created. Ultimate land use
was based on the City's comprehensive land use plan and supplemented with land use
projections made by City personnel. The landuse categories within the drainage basins are
shown in Table 2.1.
City of Dubuque, lowa Drainage Basin Master Plan
Methodologies 2-2 Fall 2001
METHODOLOGt'ES
Table 2.1
Drainage Basin Land Use Groups
ST Streets
CO Commercial
IND Industrial
INS Institutional
HD High Density Residential
MD Medium Density Residential
LD Low Density Residential
AG Agricultural
OP Open Space and Grass
2.3 HYDROLOGIC MODEL
The U.S. Army Corps of Engineers (USACE) Hydrologic Engineering Center (HEC) Hydrologic
Modeling System (HEC-HMS) was selected to model the drainage areas in the city of Dubuque.
HEC-HMS simulates precipitation-mnoff processes of dendritic drainage systems. HEC-HMS
computes runoff volume by computing the volume of water intercepted, infiltrated, stored,
evaporated, or transpired and subtracting it from the precipitation.
HEC-HMS is designed to simulate the surface runoff response of a drainage basin to
precipitation input. The model represents the basin as an interconnected system of hydrologic
and hydraulic components. Each component models an aspect of the precipitation-runoff
process within a portion of the basin commonly referred to as a subbasin. A component may be
a surface runoff entity, a stream channel, or a reservoir. The result of the modeling is the
computation of stream flow hydrographs at desired locations in the drainage area.
NRCS methodology was used to determine runoff volumes, direct runoff and channel routing.
The advantage of the NRCS methodology is it converges quickly, resulting in a very stable
model. Additionally, the input parameters are more commonly known and understood, resulting
in easier applications. The disadvantage is the results are not as accurate as for non-linear
routing, and differing land uses can only be accounted for via the runoff curve number. In the
Drainage Basin Master Plan analysis, the NRCS methodology was used.
City of Dubuque, Iowa Drainage Basin Master Plan
Methodologies 2-3 Fail 2001
191ETHODOLOGIES
Key data required by the I-IEC-HMS model include:
· Drainage basin area;
Precipitation depths;
· Runoff curve number;
· Unit hydrograph and basin lag time;
· Design storm characteristics; and
· Channel and reservoir routing parameters.
2.3.1 Model Schematic
HEC-HMS dynamically routes storm water through open channels. Hydraulic routing through
drainage systems requires a mathematical framework from which numerical calculations can
take place. HEC-HMS uses a link-node concept to idealize real-world systems. This concept
requires a network of nodes or junctions and links or reaches represent the drainage system. A
node is a discrete location in the drainage system where conservation of mass or continuity is
maintained. Links are the connections between nodes and are used to transfer or convey water
through the drainage system. The following general guidelines were used to locate nodes in the
drainage area schematic:
1. Upstream and downstream of any structure (e.g., culverts, weirs, etc.);
2. Ponds and lakes (specifically storage nodes);
3. Channel junctions;
4. Downstream boundary;
5. Where channel geometry changes abruptly;
6. Where the channel bed slope changes abruptly; and
7. Where major surface inflows to the conveyance system.
By following the general guidelines, a schematic diagram of the drainage area conveyance
system was developed. The drainage area drainage areas were delineated and subdivided using
the DAGIS mapping. The two-foot contour interval on the GIS mapping provided useful
information in determining the major drainage area divides and subbasin delineation. The
drainage area was segmented into subbasins based on selected design points.
City of Dubuque, Iowa Drainage Basin Master Plan
Methodologies 2-4 Fall 2001
M ETHODOLOGI'ES
2.3.2 NRCS Runoff Curve Number
The Natural Resources Conservation Service (NRCS) runoff curve number procedure was used
to compute abstractions for storm rainfall. Abstractions are defined as the physical process (such
as soil infiltration and detention or retention by vegetation), which effectively reduces the
volume of precipitation, which becomes runoff. The rainfall in excess of the abstractions
becomes runoff and is referred to as excess rainfall. Excess rainfall is always less than or equal
to the depth of precipitation. The curve number is a function of land use, soil type, condition of
cover, and antecedent moisture condition. This information was used in conjunction with
information from the Dubuque County Soil Survey, GIS mapping and city's drainage
standards/criteria to develop a runoff curve number for each subbasin. The soils are generally
characterized as hydrologic soil group 'B', which have moderate infiltration rates if thoroughly
wetted, and consisting of deep or well drained soils with moderately fine to coarse textures. The
average antecedent moisture condition (AMC-II) was assumed. The curve numbers are based on
the tables published by the NRCS in Technical Report 55 (TR-55). Table 2.2 summarizes the
land use classification and its respective curve number.
In subbasins where development is partially or fully developed, the hydrologic analysis was
performed for ultimate land use development. In subbasins where agricultural development was
present, the hydrologic analysis was performed as agricultural land use, because developers are
required to provide on-situ detention to maintain existing runoff releases.
Table 2.2
Drainage Area Land Use Groups and Curve Number
ST Streets 99
IND Industrial 88
CO Commercial 92
INS Institutional 88
HD High Density Residential 85
MD Medium Density Residential 75
LD Low Density Residential 72
AG Agricultural 73
OP Open Space and Grass 69
City of Dubuque, Iowa Drainage Basin Master Plan
Methodologies 2~5 Fall 2001
METHODOLOGI'ES
2.3.3 NRCS Unit Hydrograph
The unit hydrograph method is the component in the rainfall-runoff model that transforms the
rainfall excess into a surface runoff hydrograph. The unit hydrograph represents a typical
hydrograph shape for a drainage area. The unit hydrograph for a drainage area is defined as a
direct runoff hydrograph resulting from one inch of excess rainfall generated uniformly over the
drainage area at a constant rate for a storm of a specified duration.
The NRCS unit hydrograph method relates hydrograph characteristics to a physical characteristic
of the drainage area, the basin time to peak, tp. The basin time to peak is defined as the time from
the beginning of the rainfall event to the time at which the peak runoff rate is observed at the
drainage area outlet. The time to peak can be estimated using the following empirical equation:
At
tp = -~- + tlag
where:
tp ~
hag =
time to peak, in hours
computational interval, in hours
lag time, in hours
The lag time is defined as the time difference between the center of mass of the rainfall excess
and the peak of the unit hydrograph. Lag times for each subbasin within the drainage area were
computed by applying the curve number method in the GIS analysis. The lag time is give by the
following equations:
°'8 (s + 1)°''
t~ag - 1900 y0.5
1000
S = -10
CN
where:
tag = lag time, in hours
L = greatest flow length, in feet
Y = average drainage area slope, in percent
CN = runoff curve number, based on land use, land treatment and soil
type
The NRCS unit hydrograph method was utilized in the HEC-HMS model for the drainage basins
in the study.
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2.3.4 Rainfall
The 24-hour rainfall depths for the 10-, 50-, 100- year frequency shown in Table 2.3 were based
on the point (station) data and developed as isohyetal maps presented in the Midwestem Climate
Center and lllinois State Water Survey publication, Bulletin 71, "Rainfall Frequency Atlas of the
Midwest". The point data values are higher than the areal mean relations determined for each
climatic section in the state of Iowa. The hydrologic analyses were conducted using the higher,
more conservative point data values. The 500-year rainfall depth was extrapolated from the
10-, 50- and 100-year values. Area rainfall reduction factors were not used to reduce the point
rainfall depth because the drainage areas were less than 10 square miles.
Table 2.3
City of Dubuque 24-Hour Total Rainfall Depths
4.5
6.0
7.0
11.0
In order to calibrate the hydrologic model, a comparison of the basin runoff to other hydrologic
methods was made. An observed hydrograph, depicting flow rates over time, was not available
for any storm events to calibrate; therefore, another method was sought. Hydrologic analysis has
been conducted for Catfish Creek and its tributaries in the 1989 Federal Emergency Management
Agency (FEMA) Flood Insurance Study (FIS). The North Fork of Catfish Creek was the first
drainage basin to be studied; therefore, a comparison of the 100-year FIS results and 100-year
HEC-HMS results were evaluated. North Fork of Catfish Creek is an ungaged stream, so
synthetic methods were used to obtain the discharge-frequency relationships in the FIS. In
addition, the Iowa Department of Transportation's (IaDOT) regression equations were compared.
A summary of 100-year peak discharges is shown in Table 2.4.
city of Dubuque, Iowa
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Fall 2001
METHODOLOGIES
Table 2.4
North Fork Catfish Creek Peak 100-Year Discharge Comparison
at Confluence with Middle Fork Catfish Creek
I
IaDOT 2,500-3,140 Developed for rural Iowa drainage basins.
FEMA-FIS 3,600 Flood Insurance Study using regression
equations. Based on existing land use
conditions.
HEC-ItMS 2,950 Existing land use conditions with no
effective storage. Type-Il distribution.
HEC-HMS 3,200 Existing land use conditions with no
effective storage. Modified Type-II rainfall
distribution.
From Table 2.4, the IaDOT results are lower then FIS or HEC-HMS results. It is because the
IaDOT equations were derived for rural drainage basins and urban effects are not recognized. In
order to simulate the iriS discharges, modifications to the NRCS Type-II rainfall distribution
were made. The modification was performed to account for the quick runoff response of
Dubuque soils. The hyetograph for each basin was developed using a 15-minute time increment
and a modification of the NRCS Type-II rainfall distribution by including the 6-hour rainfall
hyetograph within the 24-hour hyetograph. This technique maintained the depth and timing of
the 24-hour storm while incorporating the intensity of the 6-hour storm. Table 2.5 tabulates the
modified distribution. This modification produced favorable discharges to the FIS discharges.
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Table 2.5
City of Dubuque 15-Minute Time Distribution for 24-Hour Storm Event
0.000 0.000 0.000 0.000 0.017 0.023 0.030 0.053
0,007 0.009 0.012 0.021 ,~ ')::~ 0.021 0.027 0.036 0.064
0.010 0.014 0.018 0.032 0.024 0.032 0.042 0.074
0.010 0.014 0.018 0.032 0.024 0.032 0.042 0.074
0.010 0.014 0.018 0.032 0.024 0.032 0.042 0.074
0.010 0.014 0.018 0.032 ~': ~:;m 0.028 0.036 0.058 0.085
0.010 0.014 0.018 0.032 ~;,~ 0.042 0.056 0.063 0.085
0.010 0.014 0.018 0.032 0.042 0.056 0,063 0.096
0.010 0.014 0.018 0.032 0.046 0.061 0.068 0.096
0.010 0.014 0.018 0.032 ~ 0.056 0.075 0.084 0.112
0.010 0.014 0.018 0.032 0.056 0.075 0.084 0.127
0.010 0.014 0.018 0.032 0.070 0.094 0.105 0.159
0.010 0.014 0.018 0.032 ~,~ 0.070 0.094 0,105 0.191
0.010 0.014 0.018 0.032 0.095 0.127 0.142 0:223
0.010 0.014 0.018 0.032 i~ 0.119 0.160 0.179 0.276
0.010 0.014 0.018 0.032 0.193 0.259 0.289 1.104
0.014 0.018 0.024 0.042 1.495 2.007 2.242 2,930
0.014 0.018 0.024 0.042 0.396 0.531 0.593 0.791
0.014 0.018 0.024 0.042 0.172 0.230 0.257 0.343
0.014 0.018 0.024 0.042 0.108 0.146 0.163 0,244
0.014 0.018 0.024 0.042 0.087 0.118 0.131 0.191
0.014 0.018 0.024 0.042 0.077 0.103 0.116 0.159
0.014 0.018 0.024 0.042 0.066 0.089 0.100 0,138
0.014 0.018 0.024 0.042 0.056 0.075 0.084 0.117
0.014 0.018 0.024 0.042 0.053 0.071 0.079 0.106
0.017 0.023 0.030 0.053 0.042 0.056 0.063 0.096
0.017 0.023 0.030 0.053 ~ 0.042 0.056 0.063 0.085
0.017 0.023 0.030 0.053 0.042 0.056 0.063 0.084
0.017 0.023 0.030 0.053 :9:;!~. 0.039 0.052 0.058 0.077
0.017 0.023 0.030 0.053 0.024 0.032 0.042 0.074
0.017 0.023 0.030 0.053 0.021 0.027 0.036 0.064
0.017 0.023 0.030 0.053 0.021 0.027 0.036 0.064
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Table 2.5
City of Dubuque 15-Minute Time Distribution for 24-Hour Storm Event
0.021 0.027 0.036 0.064 0.010 0.014 0.018 0.032
0.021 0.027 0.036 0.064 0.010 0.014 0.018 0.032
0.021 0.027 0.036 0.064 0.010 0.014 0.018 0.032
0.017 0,023 0.030 0.053 0.010 0.014 0.018 0.032
0.017 0.023 0.030 0.053 0.010 0.014 0.018 0.032
0.017 0.023 0.030 0.053 0.010 0.014 0.018 0.032
0.017 0.023 0.030 0.053 0.010 0.014 0.018 0.032
0.017 0.023 0.030 0.053
0.010 0.014 0.018 0.032
0.014 0.018 0.024 0.042 0.010 0.014 0.018 0.032
0.014 0.018 0.024 0.042 0.010 0.014 0.018 0.032
0.014 0.018 0.024 0.042 0.010 0.014 0.018 0.032
0.014 0.018 0.024 0.042 5,,~ 0,010 0.014 0.018 0.032
0.014 0.018 0.024 0.042 0.010 0.014 0.018 0,032
0.014 0.018 0.024 0.042 0.010 0.014 0.018 0.032
0.014 0.018 0.024 0.042 i 0.010 0.014 0.018 0.032
0.014 0.018 0.024 0.042 ~ 0.007 0.009 0.012 0.021
0.010 0.014 0.018 0.032 4.5 6.0 7.0 11.0
2.3.5 Channel Routing
Routing of flood flows from the outlet of an upstream subbasin to the next subbasin outlet was
accomplished using the Muskingum routing method in HEC-HMS. Data input for the
Muskingum consists of a storage correlation coefficient and a travel time for a reach. The storage
correlation coefficient is a measure of how closely storage in the reach is related to outflow.
Based on sensitivity analyses performed during the project it was shown to be a relatively
insensitive variable. A value of 0.2 was used throughout the study area. The travel time through
a given reach was calculated using GIS and based on an assumed velocity of 3.3 feet per second
(1 meter per second).
2.3.6 Reservoir Routing
Reservoir routing was included in the model to account for the flood attenuation effects
associated with roadway storage and existing and potential detention basins. The HEC-HMS
Modified Puls routing routines were used to simulate flow through the reservoirs using the level
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METHODOLOGTES
pool routing procedure. This procedure assumes the reservoir water surface remains effectively
level during the routing. Stage-storage-discharge relationships were developed where storage
was effective by computing a stage-outflow relationship and combining it with the stage-storage
relationship for the upstream reservoir pool. The stage-storage relationship was derived from
GIS mapping. Stage-discharge rating tables were developed using information on the outlet
works facilities obtained in the field. Assuming inlet control, a stage-discharge relationship was
generated using nomographs contained in the Federal Highway Administration's (FHWA)
Hydraulic Design Series No. 4 (HDS-4).
2.3.7 CRWR-PrePro
A preprocessor was developed by the Center for Research and Water Resources (CRWR) at the
University of Texas, Austin, under the supervision of Dr. David Maidment. CRWR-PrePro was
used to develop the input data for the hydrologic model.
CRWR-PrePro is a GIS preprocessor for the Hydrologic Engineering Center's (HEC)
Hydrologic Modeling System (HEC-HMS). HEC-HMS is currently being developed by I-~C as
part of the NexGen program of research. The purpose of CRWR-PrePro is to summarize data
from a GIS system for input to HEC-HMS. CRWR-PrePro uses stream and subbasin GtS layers
as input data. Stream and subbasin data layers are required as input, and the software requires
the use of metric units. The CRWR-PrePro analysis was executed using metric units and then
the output data, consisting of a HEC-HMS basin file, was converted to English units. The
system is written in ArcView Avenue programming language (Version 4.0.av).
The data sets must be in the same geographic coordinate system, and the input data must
accurately describe the hydrologic properties of the area. Errors occur due to discrepancies
among the stream and subbasin data layers.
The program code is oriented around identifying hydrologic elements and the relationship
between these elements. Seven (7) hydrologic elements are identified: subbasins; sources;
reaches; junctions; reservoirs; diversions and sinks.
The step-by-step methodology for developing a HEC-HMS basin file using CRWR-PrePro is
presented below. These steps produce a HEC-HMS basin file, which is then imported into HEC-
HMS.
City of Dubuque, Iowa Drainage Basin Master Plan
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Table 2.6
Spatial Data for CRWR-PrePro
DEM Digital elevation model (DEM), 10 meter ~id of elevations describing
topography, developed from the Digital Terrain Model (DTM) within the
DAGIS dataset.
Rf Shape file of streams or reaches developed by the EPA, augmented by
DAGIS data.
LU Land use shape file developed from DAGIS data.
STATSGO State Soil Geographic database, soil classifications, developed by U.S.
Geologic Survey
Aerial Photos Aerial photography used for identifying structures and other features.
1. Develop a GIS Database- Spatial data representing the basin and streams is
compiled in an ArcView project file. The required spatial data sets are shown in
Table 2.6.
2. Intersect the stream shape file with the DEM to assure the streams dehneated from
the DEM match those from the EPA reach file (Rf).
3. Fill the DEM sinks so sumps do not cause incorrect flow directions.
4. Compute the flow direction for each grid point within the DEM.
5. Compute a flow accumulation grid based on the number of cells draining to each
point.
6. Construct a stream network based on a user defined accumulation threshold.
7. Streams may be added to the stream network if they were not included in step 6.
8. Segment streams into reaches.
9. Place outlets at the junctions of each stream reach.
10. Add additional outlets where necessary (i.e. at structures).
11. Delineated drainage areas from each of the outlets using the DEM.
12. Streams and drainage area grids are converted to vector shapefiles.
13. Subbasins may be merged.
14. Calculate runoff curve numbers based on land use and soil classification.
15. Determine lag time based on basin topography.
16. Determine Muskingum coefficients based on channel characteristics.
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METHODOLOGI'ES
17. Export the data set to a HEC-HMS basin file.
18. Import the I-I~C-HMS basin file into a HEC-HMS project file.
2.4 HYDRAULIC MODELS
Hydraulic models were developed for some of the drainage basins in the city of Dubuque for the
purpose of assessing flood conditions including water surface elevations and hydraulic capacities
of existing drainage structures. Peak runoff rates computed as part of the hydrologic modeling
were used in conjunction with the GIS and limited field data to develop open channel and closed
conduit hydraulic models. For the open channel model, water surface profiles were computed for
the 10-, 50-, 100- and 500-year remm period flood events. The resulting 100-year floodplain for
ultimate development with and without project conditions was delineated using GIS. A portion
of the North Fork Catfish Creek main channel was modeled with a hydraulic model. The closed
conduit model was used to analyze the hydraulics of the Bee Branch main storm sewer trunk
line. The 10-, 50-, and 100-year return period flood events were investigated. The following
sections describe the key elements involved in the hydraulic modeling of the stream segments in
the City of Dubuque.
The Hydrologic Engineering Center - River Analysis System (HEC-RAS) was used to analyze
open channel hydraulics. HEC-RAS is a hydraulic model developed by the U.S. Army Corps of
Engineers. The model is designed to perform one-dimensional hydraulic calculations for a
network of natural and constructed open channels. The following assumptions are used by HEC-
RAS in computing water surface profiles:
· Steady flow;
· Gradually varied flow;
· One-dimensional flow;
· Channel slopes are small, less than 1:10
Although some of the steeper channels may exhibit supercritical flow characteristics, it is
conservative to base the hydraulic analyses on subcritical flow, since the depth of flow for
subcritical flow conditions is greater than supercritical flow conditions.
XP-SWMM was used to analyze closed conduit hydraulics. XP-SWMM is proprietary storm
water modeling software based on the U.S. Environmental Protection Agency model SWMM
(Storm Water Management Model). XP-SWMM is capable of modeling unsteady flow allowing
for analysis of changes in flow variables with time and attenuation of peak discharges as a result
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~ETHODOLOG~'ES
of storage. The following assumptions are used in hydraulic computations performed by XP-
SWMM:
· Gradually varied flow;
· One-dimensional flow; and
· Subcritical flow
2.4.:[ Model Schematic
For the open channel model, channel cross-section geometry and flow lengths were obtained
from a triangular irregular model (TIN) developed from the digital terrain model (DTM). Cross-
section geometry was generated from the TIN and the U.S. Army Corps of Engineer's HEC-
GeoRAS software in conjunction with ArcView's 3D-Analyst which electronically generates the
I-IEC-RAS input files within ArcView. Bridge and culvert geometry were obtained from field
measurements. Manning's roughness coefficients were selected based on field observations and
interpretations from aerial mapping. Guidelines contained in "Open Channel Hydraulics," by
Chow, were used when estimating roughness coefficients.
The closed conduit XP-SWMM model was generated based primarily on information supplied
by the City. The DAGIS storm sewer coverage provided the storm sewer alignment in the area
of interest, and model geometry was based on storm sewer profile sheets with additional
information obtained from the City's archive. Manning's roughness coefficients were selected
based on conduit material information taken from storm sewer profile sheets and
recommendations made by City engineering staff. Guidelines contained in "Open Channel
Hydraulics," by Chow, were used when estimating roughness coefficients.
2.4,2 Model Calibration
Several high-water marks were evaluated for the May 16, 1999 storm event. This 1999 storm
was estimated to be a 75-year remm period. High-water marks were used for an order of
magnitude assessment of the model results. No additional calibration of the hydraulic model was
performed.
2.4.3 Channel and Structure Improvements
Channel improvements were evaluated for a number of problem areas identified in the study.
HEC-RAS offers a convenient method for analyzing a range of channel improvement options
and includes computational procedures for estimating excavation volumes and computing
City of Dubuque, Iowa Drainage Basin Master Plan
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METHODOLOGIES
revised flood levels with the channel improvement in place. Channel shaping and clearing
improvements were considered in several reaches of the study area.
Storm sewer improvements involved expansion of storage and conveyance through installation
of additional conduits or construction of flood control channels. Improvements were iteratively
incorporated into the XP-SWMM model and analyzed to assess their impact on flooding.
2.4.4 Drainage Criteria
The city plans to adopt drainage standards/criteria to be used as a guidance document for
designing and evaluating drainage facilities within the city's jurisdiction. Storm drainage
systems shall be designed to convey runoff from a return period storm, dependent on the type of
drainage system facility.
In addition to providing storm drainage facilities for the design runoff, drainage policies dictate
that provision shall be made to prevent significant property damage and loss of life from the 100-
year remm period storm.
2.4.5 Cost Estimates
Cost estimates were developed for recommended improvements at each of the problem areas
identified on the major storm drainage system considered in the study. Component costs were
estimated based on typical unit costs for construction. Contingencies (25%) were added to
account for estimated quantities, unit price adjustments and miscellaneous work related items.
An additional 25% was included for administrative, legal and engineering costs. Right-of-way,
operation and maintenance and mitigation costs were not included.
Unit costs for specific components of improvement projects were obtained from the Iowa
Department of Transportation 1999 bid tabulations. Unit price adjustments were made for large
projects to account for economy of scale.
2.5 WATER QUALITY
Erosion and sedimentation processes are natural processes accelerated by human activities,
especially during construction. Reducing erosion and preventing sediment from leaving
construction sites offers the best opportunity to improve water quality of the environment.
Rainfall on unprotected soil causes serious erosion and results in sediment being deposited in
drainageways and a general degradation of the environment.
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I~IETHODOLOGTES
One major component of managing storm water runoff is the implementation of Best
Management Practices (BMPs). Iowa State University has published an erosion control manual
for construction site measures entitled "Iowa Construction Site Erosion Control Manual". The
manual is to serve as a guide in selecting erosion control practices and preparing plans to reduce
erosion on construction sites.
BMPs are operational techniques and/or structural facilities that can dramatically improve the
quality of storm water runoff. Operational BMPs reduce the opportunity for pollution to come
into contact with storm water mnoff, whereas structural BMPs collect, concentrate, and/or treat
mnoff. The costs to implement operational and/or structural BMPs are usually significantly less
than the costs associated with remediation damage resulting from inadequate storm water
management. Operational BMPs are much more economical and simplistic, so they should
generally be considered before structural BMPs.
When selecting any type of BMP, non-technical issues, as well as technical issues, should be
considered. Technical issues vary with individual BMPs, but broadly deal with site feasibility,
design considerations, and/or pollutant removal efficiencies. Technical issues are generally more
involved for slructural BMPs than operational BMPs. Non-technical issues deal with the
economic, regulatory, and public aspects of selecting a BMP. These issues, among others,
include: federal, state, and local regulations; real and perceived receiving water problems;
economic feasibility of BMP being considered and public acceptance of BMP being considered.
2.5.:L Operational Bl~lPs
The goals of operational BMPs are to prevent pollutants from coming in contact with storm
water by controlling the pollutants at their source. For this reason, operational BMPs are often
referred to as source control BMPs. Operational BMPs are non-structural controls generally
associated with management practices that reduce contact between storm water and pollutants.
The effectiveness of operational BMPs is often highly dependent on site-specific conditions, due
to the high variability in pollutant source conditions; thus it is difficult to generate general
removal efficiencies. Source controls for urban areas can be grouped into the following general
categories:
· Public education
· Street/storm drain system maintenance
· On-site materials management
· Planning and regional management
· Illicit/accidental controls
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Public education can be one of the most economical and effective pollution control strategies.
The goal of public education is to change the way the public manages many of the constituents
that end up in storm water runoff, through awareness. The methods in which many household
products such as automotive fluids, cleaners, and fertilizers are used and disposed of can have a
profound effect on the quantities of these substances that come into contact with storm water,
and thus on the water quality of receiving waters. Many methods available for increasing public
education include radio/television advertisements, mailings, public meetings, and others.
Although public education is one of the simplest means of affecting storm water quality, its
effectiveness is highly variable, and may be hard to directly measure.
Street and storm drain maintenance refers to the removal of pollutants from street surfaces and
the periodic cleaning of storm drainage structures. This control may reduce the quantity of
pollutants, most notably sediment, entering the storm sewer system. Examples of this type of
pollution control include street sweeping, catch basin cleaning, curb and gutter cleaning, and
road and bridge maintenance.
On-site materials management deals with the practice of use, storage, and disposal of substances
that could pollute storm water runoff. There are many specific pollution controls for materials
management; however, they can be generalized into three groups:
· Altering the activity to minimize generation of potential pollutants
· Covering pollutant sources, thus reducing their contact with precipitation and runoff
· Containing/segregating the activity containing source of pollutants from other
activities, so pollutants may be handled and disposed of separately
Examples of on-site materials management include: storing materials inside or under cover on
paved surfaces, minimizing storage and handling of hazardous materials, secondary containment
to reduce leakage, and choosing safer alternative products.
Planning and regional management refers to practices by local governments aimed at reducing
pollutants in storm water on a regional basis, especially those loadings from new development
areas. Land use controls and floodplain management practices are the typical mechanisms for
this type of pollution control. Examples of planning and regional management include: buffers
and setbacks from all water bodies, zoning ordinances for open areas, regulations for sediment
control measures in new developments, and use of vegetated natural channels.
Illicit and accidental control BMPs can be used to reduce introduction of pollutants to storm
sewer systems through illegal or accidental activities. These activities are often related, because
a responsible party may not even be aware of the detrimental impacts of an illegal or accidental
discharge to the storm sewer system. Examples of illicit and accidental controls include:
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METHODOLOGIES
detection, removal, and enforcement system for illegal connections/dumping through inspections
or source testing; public notices; and accidental spill information boards/hotlines.
2.5.2 Structural BMPs
The goal of structural BMPs is to reduce non-point source pollution by collecting, concentrating,
and/or treating storm water runoff. Unlike operational BMPs, which are often simply techniques
for source control, structural BMPs are physical entities that are strategically located within a
drainage area. The benefit of having purposefully located and designed entities is that it
facilitates tabulation of general pollutant removal efficiencies for different structural BMPs.
However, the disadvantages are higher initial cost, more complexity, and required maintenance.
Overall, structural BMPs are most applicable to developing and redeveloping areas, since
construction/implementation costs are less and site location is easier.
Structural BMPs are strategically located and designed to maximize their beneficial impact on
storm water quality for an area, and to minimize implementation and operational costs. This
benefit/cost feasibility analysis for selecting a structural BMP can be grouped into five general
categories:
· Physical suitability
· Hydrologic conditions
· Pollutant characteristics and removal capabilities
· Environmental and aesthetic factors
· Operational factors
Physical suitability of a site refers to the technical feasibility criteria related to physical
conditions, such as topography, required land area, contributing drainage area, soil types, and
water availability. Physical suitability is often one of the first considerations when selecting a
structural BMP since it is not feasible or possible to change many of the factors, and it can
dramatically affect the usefulness of a given BMP.
Hydrologic criteria focus on the hydrologic characteristics for a given design storm event, such
as storm water runoff volume, distribution, and peak discharge. It should be noted that the
concepts in designing water quality controls are different than those for water quantity controls.
The highest concentrations of pollutants are often found in the beginning of storms, often
referred to as the "first flush" stage. In this stage, built-up pollutants are being washed off the
land surface and potential dilution effects are negligible. Thus, water quality controls are
designed for smaller, more frequent storms, whereas water quantity controls focus on larger, less
frequent storms, which cause flooding and other damage.
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Environmental and aesthetic factors refer to the impacts a structural BMP would have on the
environment- how it would affect the aesthetics of the area. Examples of environmental and
aesthetic factors include maintenance of low flows for aquatic life, streambank erosion,
recreational benefits, and community acceptance.
Operational factors are mainly concerned with the amount and type of maintenance a given
structural BMP requires. Generally, structural BMPs have a passive design, meaning that there
is no active operation of mechanical or chemical equipment. However, almost all structural
BMPs require periodic cleaning and maintenance to keep them working efficiently.
The following list includes a number of different structural BMPs that are commonly used to
improve water quality of storm water runoff:
· Swales
· Filter strips and vegetative buffer zones
· Infiltration basins and percolation trenches
· Detention controls and constructed wetland basins
· Oil and water separators
Swales are shallow, vegetated, mildly- sloped channels that convey storm water runoff. They are
designed for low velocity flows during small storms to allow infiltration of storm water into the
swale bottom, and filtration and biological uptake of pollutants into the vegetative cover-
collectively referred to as biofiltration. Swales are applicable in most mildly sloping areas, due
to their relatively low space, cost, and maintenance requirements.
Filter strips are similar to swales, except they do not have side slopes, thus runoff is spread
evenly through the filter strip area as sheet flow, rather than through small channels. Treatment,
cost, maintenance, and applicability are similar to those of swales. Vegetative buffer zones are a
specific type of filter strip surrounding or "buffering" a water body, so as to remove pollutants
before reaching the receiving body.
Infiltration basins and percolation trenches are systems that enhance the potential for storm water
runoff to percolate into the soil. These systems consist of a structure or trench filled with a filter
media such as sand or gravel, which allows percolation into the soil. Infiltration basins and
percolation trenches only work with porous soils, favorable site geology, and proper groundwater
conditions. Infiltration devices are generally effective in the Dubuque area unless the silt loam
layer is shallow and under lain by bedrock.
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Detention controls consist of both dry detention basins, which completely drain out between
storm events, and wet retention ponds, which maintain a designed level of water between storm
events. Constructed wetland basins are complex wet retention facilities that have additional
construction and biological requirements, but often provide increased pollutant removal. The
primary mechanism for pollutant removal is sedimentation. Wet retention ponds provide
additional removal through physical and biochemical processes, such as reduction in bottom
scour and increased vegetative growth in the permanent pool. In addition to good pollutant
removal, detention facihties also can provide reduction in peak runoff flows. Detention controls
are most applicable where relatively large tracts of land are available, such as parks and
industrial facilities.
2.6 DEVELOPMENT OF RECOMMENDED PLAN
2.6.1 General
Investigations of structural flooding and roadway overtopping were conducted for the future
development conditions. Runoff from the future conditions was routed through the existing
channels, culverts, and storm drains.
2.6.2 Structural Flooding
A 100-year floodplain delineation was created in ArcView using the existing conveyance
elements and the ultimate land use runoff estimates for the segment of channels analyzed. Using
the GIS topographic coverage and the 100-year floodplain, flooded structures were identified.
Finished floor elevations were not surveyed.
2.6.3 Roadway Overtopping
Roadway overtopping is defined as transverse flow over a roadway resulting from flooding of an
adjacent channel. Roadway overtopping was estimated for the 10-, 50- and 100-year storms.
Roadway crest elevations were determined from the 1999 City of Dubuque 2-foot contour maps
and the TIN generated from the City DTM. A majority of the roadway crest elevations at creek
and tributary crossings were identified by survey using spot elevations. These spot elevations
were verified by interpolation between roadway GIS contours at crossing locations.
City of Dubuque, Iowa Drainage Basin Master Plan
Methodologies 2-20 Fall 2001
METHODOLOGIES
Roadways adjacent to or crossing the storm drainage system were classified as residential,
collector, minor arterial, and principal arterial. Roadway classifications were established using
the following general definitions:
· Residential - interior streets in subdivisions and residential areas
· Collector - streets that direct subdivision and residential traffic to arterial roadways
· Minor Arterial - major streets directing collector traffic to other collector streets and
freeways
· Principal Arterial - any U.S. or state designated roadway
The road~vay overtopping criteria are summarized below in Table 2.7. In this table, the design
storm is the flood event the culvert or storm sewer must pass to meet the criteria. For example, a
residential roadway cannot flood in the 10-year storm to meet the criteria but may flood in the
50-year storm.
Table 2.7
Roadway Overtopping Design Storms
Residential 10 No maximum
Collector 50 1.5
Minor Arterial 50 1.0
Principal Arterial 100 0.0
2.6.4 Flood Minimization Alternative Improvements
A list of flood minimization alternatives was compiled based on experience from past master
planning and flood control activities with consideration for the unique topography in and around
the City of Dubuque. Alternatives considered to have potential benefit in the City of Dubuque
are shown in Table 2.8. A brief discussion of each alternative is given below.
City of Dubuque, lowa Drainage Basin Master Plan
Methodologies 2-21 Fail 2001
~IETHODOLOGTES
Table 2.8
Flood Minimization Alternative Improvements
Public Education/Outreach Rehabilitate/Expand Capacity of Existing Facilities
Floodplain Buyout Create Upstream Detention
Flood Proofing Flood Control Channel
Flood Warning System Relief Storm Sewer
Do Nothing Transbasin Diversion
Deep Storage/Pumping Tunnel
Pressure Sewer System
2.6.4.1 Nonstructural Alternatives
Nonstmctuml alternatives focus on minimization of property damage or loss of life through
means other than construction of detention and conveyance facilities. They involve public
awareness of flood dangers, protection of property from flood damages, and removal of
individnals from flood prone areas.
Public Education/Outreach
Public education programs can be instrumental in reducing flood losses and future flood
causalities. Public outreach can include a development of public programs to provide emergency
shelters and first aid during a flood event, emergency services to assist in evacuation of
residences, and educational programs intended to inform citizens of required safety practices
before, during, and after a flood event.
Floodplain Bu¥out
After the delineation of the 100-year limits of flooding, a program to acquire and remove flood-
prone structures may be feasible in reducing or eliminating flooding problems. This approach
may be considered for clearing the entire floodplain or as a partial solution in isolated areas
where coverage by a structural solution exceeds the value of isolated structures. Floodplain
acquisition programs have been used successfully in many communities and may be useful in
reducing flood hazards in Dubuque.
Flood Proof'mg
When structural flood control alternatives are found to be cost prohibitive, flood proofing is an
alternative that should be considered to reduce flood impacts. Installation of a variety of flood
proofing systems would be required in order to meet the varied needs of the structures located
within the flood-prone areas. Flood proofing facilities may range from structural modifications
City of Dubuque, lowa Drainage Basin Master Plan
Methodologies 2-22 Fall 2001
METHODOLOGY'ES
to reduce or eliminate damages from flooding to educational programs informing citizens how to
protect their property or remain safe during a flood event.
Structural measures are usually implemented in commemial or industrial settings where
personnel are available to operate and maintain flood proofing devices. In residential
applications, flood proofing is typically limited to the relocation of vital residential systems such
as heating, cooling, water heaters and laundry areas to safe flooding areas. The relocation of
electrical services to areas above the anticipated water surface elevation also is required.
Frequently casualties during flooding relate to structural failures of basement and foundation
walls. Public education is an effective means to inform people of these dangers.
Flood Warning System
A flood warning system would be a critical element to the development of a flood proofing
strategy. Flood warning systems can be designed to provide advance notice of a potential flood
event by installing flood monitoring, rainfall indicators and storm sewer flow monitors in
upstream areas. In the City of Dubuque, a flood warning system could be utilized to monitor
flood conditions in various detention facilities including Ice Harbor, Maus Lake, the 16th Street
Detention Cell and the West 32nd Street Detention Cell. This information would be valuable for
managing operations such as pumping and gate closure operations as well as provide information
as to when flood warning alarms should be sounded.
Because of the steep basins and high rate of storm water runoff in Dubuque, a flood warning
system would not provide a meaningful amount of time. The City also should consider the
possibility that a flood warning system may encourage people to leave their homes and try to
evacuate when such evacuation is not possible due to the short notice time and high congestion
of the area. If the flood warning system were used, it would be important to provide a public
educationIoutreach program that would inform the people of the correct responses to the flood
warning system.
Do Nothing
If the public is not concerned about the frequency and magnitude of flooding problems in the
community, no action is an alternative. Flooding problems should be monitored and appropriate
steps taken to eliminate the loss of life.
2.6.4.2 Structural Improvement Alternatives
Structural alternatives involve the construction or improvement of municipal facilities with the
specific purpose of limiting the extent and depth of flooding and thereby reducing the potential
for property damage or loss of life. Structural alternatives include detention areas to capture
City of Dubuque, Iowa Drainage Basin Master Plan
Methodologies 2-23 Fall 2001
METHODOLOGi'ES
runoff, expansion of conveyance through flood prone areas, or redirection of flood flows away
from populated areas.
Rehabilitate/Expand Capacity of ExiSting Facilities
Increasing the volume of existing detention cells or modifying detention cell outlet works to
discharge flood flows could have a significant effect on flooding. Detention of larger volumes of
water in the upland areas of the City would reduce flooding in low areas near the Mississippi
River and provide relief for storm sewer systems unable to convey runoff from extreme storm
events. Increase in volume or the size of gravity outlets and pumps in detention cells adjacent to
the Mississippi River would draw water out of the Couler Valley area and discharge it to the
Mississippi River more quickly, thereby further reducing flooding depths.
Repair or replacement of storm water conveyance systems where development has exceeded the
system's capacity could decrease or eliminate flooding problems due to ponding in both the
upland and lowland areas.
Create Upstream Detention
Creation of detention in undeveloped, upland areas would decrease peak discharges and delay
the large volume of storm water runoff draining toward the Couler Valley area. Detention could
be created by constructing embankments to contain the water in the steep valleys and ravines
characteristic of the terrain in the Dubuque area. When an upstream open space is not available
for the development of detention, it becomes necessary to identify occupied sites that can be
converted to potential storage locations.
Flood Control Channel
Conveyahce of runoff through flat, heavily developed areas may require capacity in excess of
what can be provided by a closed-conduit storm sewer system. Construction of a large flood
control channel through the developed areas would provide a significant increase in conveyance
and storage and could have a large impact of the flooding problem. This requires the purchase of
private and commercial property and the relocation of individuals, businesses, roads, and
utilities. Investigations should also be undertaken to ensure the pathways runoff takes during the
design flood event to reach the flood control channel are non-damaging pathways.
Relief Storm Sewer
Construction of a relief storm sewer to expand the capacity of major trunk lines in the system
would have a similar, although less dramatic, effect than a flood control channel. The increase in
conveyance would deliver water to the Mississippi River more quickly and decrease flooding in
City of Dubuque, Iowa Drainage Basin Master Plan
Methodologies 2-24 Fall 2001
I~IETHODOLOGI'ES
the low-lying areas. The benefit/cost ratio would be substantially lower than that of the flood
control channel; however, its construction would have a less dramatic effect on the community.
Transbasin Diversion
Rather than convey runoff from the upland areas through the heavily developed areas, water
could be diverted away and allowed to take another path to the Mississippi River. One such
opportunity would be the diversion of flows entering the Couier Valley area from the north to the
Little Maquoketa River.
Deep Storage/Pumping Tunnel
Considering current tunneling technologies, the construction of a deep tunnel far beneath the
surface is an alternative that may be considered. This alternative would construct a facility
consisting of a large diameter tunnel shaft in the lowland area of the city to be used as an
underground storage reservoir. Existing sewers could be connected to this facility by service
shafts at appropriate high flow connection points. A pumping station would be required to
evacuate the system after storm events. This type of facility would be technically very
challenging; however, it would provide minimal impact to existing development and utilities.
Pressure Sewer System
An effective alternative to reduce downstream flooding would be to provide piping from upland
areas that transport large volumes of floodwater directly to the Mississippi River and bypassing
the 16th Street Detention Cell. These new sewers would likely be located in the existing street
rights-of-way and would require extensive reconstruction of existing utilities as well as street
surfacing reconstruction. To minimize the impact of construction on existing facilities, the
pressure sewer system could also be constructed using rock/earth tunneling technology.
City of Dubuque, Iowa Drainage Basin Master Plan
Methodologies 2-25 Fall 2001
NORTH FORK CATFi'SH CREEK DRAI'NAGE BASI'N
3.0 NORTH FORK CATFISH CREEK DRATNAGE BASI'N
3.1 GENERAL DRAI'NAGE BASTN DESCRZPTi'ON
The North Fork Catfish Creek (North Fork) Drainage Basin is located in the southern vicinity of
the Dubuque municipal limits and is shown on Figure 3-1. The drainage basin measures
approximately 3.9 square miles, with a majority of the drainage area being contained within the
Dubuque boundary limits. A small portion in the west part of the drainage basin extends into the
City of Asbury's jurisdiction. The drainage area is roughly bounded by Asbury Road to the
north, Pennsylvania Avenue, University Avenue and Brnnskill Road to the south, Radford Road
to the west and Grandview Avenue to the east.
The North Fork Drainage Basin is relatively steep, with an average terrain slope of around 6
pement. The overall slope of the main channel is approximately 1 percent. Elevations in the
drainage basin range from 680 ft NGVD at the confluence of North Fork with Middle Fork
Catfish Creek to 950 ft NGVD in the upper reaches of the drainage basin. Figure 3-2 shows the
range of slopes for the North Fork Drainage Basin. The steepest slopes of 15% or greater are
located along the main channel and near the confluence with Middle Fork Catfish Creek.
Information on the soil types and characteristics in the North Fork Drainage Basin was compiled
by developing a digital soils database in GIS. Table 3.1 shows the relative representation and
general hydrologic characteristics for the different soil series found in the North Fork Drainage
Basin. The North Fork Drainage Basin consists of over 25 different soil types, of which the
Fayette-Urban land complex and the Rozetta-Eleroy silt loam series account for close to 50
percent of the total drainage basin area. The majority of the Fayette-Urban series are located in
the lower two-thirds of the drainage area while the Rozetta-Eleroy series are primarily located
along the channel west of Northwest Arterial and north of Hillcrest Road. For modeling
purposes, the different soil types were grouped by the NRCS hydrologic soil type as Type A, B,
C, or D. Nearly the entire drainage basin consists of Type B soils, as depicted in Figure 3-3.
City of Dubuque, lowa Drainage Basin Master Plan
North Fork Catfish Creek Drainage Basin 3-1 Fall 2001
NORTH FORK CATFI'SH CREEK DRAI'NAGE BASI'N
Table 3.1
North Fork Catfish Creek Drainage Basin
Soil Type Summary
Fayette-Urban (5 to 14% slopes) Moderately sloping Silt 17 37.6
(4163C, 4163D) well-drained soil on short, convex side Loam
slopes in the uplands. Moderate
: permeability with rapid runoff.
Rozetta-Eleroy (9 to 18% slopes) Moderately eroded, Silt 18 9
(563E2, 563D2) strongly sloping, moderately well drained Loam
soils on convex side slopes of the uplands.
Rozetta soil on the upland areas and
Eleroy adjacent to drainageways.
Moderate permeability with rapid rtmoff.
Orthents Gently sloping soils in cut and fill areas, Loam 11 7.7
(5040B) highly variable drainage, moderate to
slow permeability, ranoff is slow to
medium
Fayette Silt (5 to 14 % slopes) Moderately eroded, Silt 46 7.3
Loam (163C2, moderately sloping, well drained, Loam
163D2) moderate permeability, medittm runoff
Various soils, 18 soil types ranging from Silt 84 38.4
0.01% to 4.5% area. Loam
Total Percent Area 100.0 %
Source: Soil Survey of Dubuque Count~, Iowa; SCS, December 1985.
The drainage system in the North Fork Drainage Basin consists of both natural channel and
closed conduit sections. The main channel is a namrai earthen channel and numerous storm
sewers convey runoff to the natural channel. The majority of the storm water conveyance system
consists of open channels, and the 18 miles of the drainage system modeled consist entirely of
open channel sections. Of the total 18 miles of conveyance length modeled, 11 miles are major
creeks and tributaries. The remaining 7 miles are smaller tributaries and drainageways.
Although there are a number of smaller creeks in the North Fork Drainage Basin, North Fork is
the only major creek. The flooding problems in the North Fork Drainage Basin are confined to
the open channels system; therefore, the storm sewer system was not modeled.
A land use database containing information for ultimate development was created based on the
DAGIS 1999 Comprehensive Land Use Plan and supplemented with land use projections made
by City staff. Land use classifications in North Fork range from open spaces to industrial, with
the majority of the drainage basin being classified as low density and medium density residential
City of Dubuque, Iowa Drainage Basin Master Plan
North Fork Catfish Creek Drainage Basin 3-2 Fall 2001
NORTH FORK CATFI'SH CREEK DRAI'NAGE BASI'N
and commercial land uses. The breakdown of land use within the North Fork Drainage Basin for
ultimate development is shown in Table 3.2 and Figure 3.4.
Table 3.2
North Fork Catfish Creek Drainage Basin
Land Use Summary
Streets 235 9.2
Industrial 6 0.2
Commercial 345 13.5
Institutional139 5.5
High Density Residential 119 4.7
Medium Density Residential 396 15.6
Low Density Residential 808 31.7
Agricultural 190 7.5
Open Space and Grass 307 12.1
Total 2,545 100.0%
Source: City of Dubuque, Iowa Comprehensive Land Use Plan, 1999.
Note: Water bodies are incorporated into adjacent parcel land use categories.
Few flood control measures have been implemented in the North Fork Drainage Basin, other
than minor channel modifications on the main channel and some of the tributaries. The North
Fork Drainage Basin is one of the few drainage basins in which regional detention of storm water
runoff may be a viable alternative for flood control. Regional detention is most effective when
applied in the upper portions of the drainage basin. Natural detention upstream of several
drainage structures offers an opportunity to reduce the discharge and water surface elevations
downstream. As the drainage basin becomes more developed, the number of available detention
sites is reduced and detention options are thereby eliminated. Regional detention sites were
analyzed along with channel improvements that can be implemented as a potential means of
flood control in the North Fork Drainage Basin.
3.2 FLOOD HYDROLOGY
The I-IEC-HMS model was utilized to compute the peak runoff rates for the 10-year, 50-year,
100-year and 500-year return period storm events. Runoff hydrographs were developed for each
storm event for ultimate development condition, as defined by the City's comprehensive land use
plan. Figure 3-5 depicts the subbasin delineation, while Figure 3-6 is a schematic of the I-]~C-
HMS model for the North Fork Drainage Basin.
City of Dubuque, Iowa Drainage Basin Master Plan
North Fork Ca~sh Creek Drainage Basin 3-3 Fall 2001
NORTH FORK CATFISH CREEK DRAI'NAGE BASi'N
Table 3.3 provides a summary of ultimate peak runoff rates for selected storm events at key
locations in the North Fork Drainage Basin. A summary of the peak runoff rates for all sub-basin
hydrographs can be found in the Hydrologic and Hydraulic Appendices.
Table 3.3
North Fork Catfish Creek Drainage Basin
Peak Runoff Summary for Existing Drainage System Conditions
Main Channel
NF-ST-1 26 Brunskill Road
NF-ST-2 22 US 20 (Dodge St.)
NF-ST-3 49 University Ave.
NF-ST-4s 18 J.F. Kennedy Rd. &
Pennsylvania Ave.
NF-ST-5 9 I Keyway
NF-ST-6 35 Rosemont St.
NF-ST-7 10 Northwest Arterial
NF-ST-8 36 Sunnyslope
NF-ST-9 3 Radford Road
NF-ST-10 5 Saratoga Road
Tributary No. 1
3.8
3.2
3.0
2.1
1.7
0.94
1,930
1,680
1,630
1,400
1,230
660
2,720
2,210
2,150
1,880
1,900
930
3,130
2,490
2,420
2,080
2,280
1,070
0.52 240 460 650
0.26 460 670 770
0.16 270 400 470
130
i 0.06
90
160
4,220
3,000
2,930
2,580
3,250
1,930
1,160
1,080
66O
23O
NF-T1-ST-1
NF-T 1 -ST-2
57 Brtmsldll Road
54 US 20 (Dodge St.)
0.41 460 850
710
270
1,240
0.14 170 320 470
Tributarv No. 2
NF-T2-ST-1 370 650 800
NF-T2-ST-2
NF-T2-ST-3
33 Hillcrest Road 0.41
30 Asbury Road 0.15
29 Asbury Road 0.03
180
290
36O
30 50 60
46O
1,230
550
100
Tributary No. 3
NF-T3-ST- 1 12 NW Arterial 0.21 270 390
NF-T3-ST-2 13 Embassy West Dr. 0.10 110 170
Notes:
1. Peak runoff rates based on ultimate land use condition and simulation of a 24-hour storm event.
2. See Figore 3-1 for location of stmctare identification number.
3. See Figure 3-6 for location of HEC-HMS node and identification number.
4.. Peak discharges reported are outflows from the specified nodes.
5.
210
55O
300
Peak discharges are attenuated by storage upstream of the Pennsylvania Avenue roadway embankment and flooding of the
J. F. Kennedy Road/Pennsylvania Avenue intersection.
City of Dubuque, lowa Drainage Basin Master Plan
North Fork Catfish Creek Drainage Basin 3-4 Fall 2001
NORTH FORK CATFI'SH CREEK DRAI'NAGE BASI'N
3.3 STREAM HYDRAULICS
HEC-HMS and HI2C-RAS were used to determine the stream hydraulics of the channel and the
bridges and culverts on the main channel and tributaries studied. A total of 16 road crossings
were analyzed in the North Fork Drainage Basin. A summary of the hydraulic capacity for each
of the crossings studied is presented in Table 3.4 for the 10-, 50- and 100-year storm events.
Table 3.4
North Fork Catfish Creek Drainage Basin
Existing Hydraulic Capacity of Stream Crossings Summary
Main Channel
NF-ST-1
Brtmskill Road
NF-ST-2 US 20 (Dodge Street)
NF-ST-3 University Avenue
J.F. Kennedy Road &
Pennsylvania Avefi
704.4
758.2 0.0
743.9 0.0
NF-ST-4
780
0.0
NF-ST-5 Keyway3 789 1.3
NF-ST-6 Rosemont Street~ 812.74 1.5
NF~ST-7 Northwest Arterial
NF-ST-8 Sunnyslope
NF-ST-9 Radford Road
NF-ST-10 Saratoga Road
835.6 0.0
858.44 0.0
864.24 0.0
No h, draulic analysis required.
Tributary No. 1
869.94
1.1
0.0 0.0
0.0 0.0
0.9 3.4
2.1 2.4
1.9 2.4
1.2 1.7
0.2 0.4
0.2 0.3
1.2 1.2
NF-T 1-ST-1 Brtmskill Road 703.84 0.0 0.0 0.0
NF-T1-ST-2 US 20 (Dodge St.) 814.9 0.0 0.0 0.0
Tributar~ No. 2
NF-T2-ST-1
NF-T2-ST-2
NF-T2-ST-3
Hillcrest Road
Asbury Road
Asbury Road
810.8
855.8
900.14
0.0
0.0
0.0
0.1 I 0.5
0.2 0.3
0.0 0.0
Tributary No. 3
NF-T3-ST-t 835.6 0.0
NF-T3-ST-2 843.14 0.0
NW Arterial
Embassy West Drive
0.0 0.0
0.0 0.0
1. Minimum overtopping depth elevation based on topo~-aphic survey, unless otherwise noted.
2. Depth of overtopping obtained from HEC-HMS analysis, unless otherwise noted.
3. Depth of overtopping based on HEC-RAS analysis.
4. Minimum overtopping elevation based on minimum roadway elevation obtained by interpolatthg DAGIS mapping.
City of Dubuque, lowa Drainage Basin Master Plan
North Fork Catfish Creek Drainage Basin 3-5 Fall 2001
NORTH FORK CATFI'SH CREEK DRAI'NAGE BASI'N
The standards/criteria for passing the design flood event without roadway overtopping were used
to evaluate each crossing. A summary of the hydraulic capacity and return period for each of the
crossings studied is presented in Table 3.5.
Table 3.5
North Fork Catfish Creek Drainage Basin
Existing Hydraulic Capacity and Return Period of Stream Crossings Smnmary
Main Channel
NF-ST-I : Brunskill Road Bridge Collector No hydraulic analysis required.
NF~ST-2 US 20 (Dodge St.) 26.8' x 18.5' Principal Arterial 100-yr with 0' GT 100-yr
CAP overtop
NF-ST-3 University Avenue t2' x 12.2' Minor 50-yr with 1' GT t00:yr
RCB Arterial overtop for
i00-yr
NF-ST-4 J.F. Kennedy Road 14.5 CMP Principal Arterial 100-yr with 0' 0.9' overtop for
& Pennsylvania overtop 50-yr & 3.4' for
Ave. 100-yr
NF-ST-5 Keyway 2- 6.5' RCP Collector 50-yr with 1.5' 2.1' overtop for
overtop for 50-yr & 2.4' for
100-yr 100-yr
NF-ST-6 Rosemont Street 6' RCP Collector 50-yr with 1.5' 1.9' overtop for
overtop for 50-yr & 2.4' for
100-yr 100-yr
NF-ST-7 Northwest Arterial 6' RCP Principal Arterial 100-yr with 0' 1.2' overtop for
overtop 50-yr & 1.7' for
100-yr
NF-ST-8 Sunnyslope 3- 4' RCP Residential 10-yr with no 10-yr with 0.4'
100-yr max. overtop for 100-
overtop yr
NF-ST-9 Radford Road 2- 3.5' RCP Collector 50-yr with 1.5' 0.2' overtop for
overtop for 50-yr & 0.3' for
100-yr 100-yr
NF-ST-10 Saratoga Road 30" RCP/3' Residential 10-yr with no 1.1' overtop for
RCP 100-yr max. 10-yr & 1.2' for
overtop 50-yr
Tributary No. 1
NF-T1-ST-1 Bransk~ll Road 9.75' x 5.6' Collector 50-yr with 1' GT 100-yr
RCB overtop for
100-~
NF-T1-ST-2 US 20 (Dodge St.) 4'-9' × 6'-1" Principal Arterial 100-yr with 0' GT 100-yr
RCAP/ overtop
4.9' x 5.8'
RCB
City of Dubuque, Iowa Drainage Basin Master Plan
North Fork Ca~sh Creek Drainage Basin 3-6 Fall 2001
NORTH FORK CATFi'SH CREEK DRAZNAGE BASI'N
Table 3.5
North Fork Catfish Creek Drainage Basin
Existing Hydraulic Capacity and Return Period of Stream Crossings Summary
Tributar~ No. 2
NF-T2-ST-1 Hillcrest Road 7' RCP Collector 50-yr with 1.5' 0.1' overtop for
overtop for 50-yr & 0.5' for
100-yr 100-yr
NF-T2-ST-2 Asbnry Road 5' RCP Minor 50-yr with 1' 0.2' overtop for
Arterial overtop for 50-yr & 0.3' for
100-yr 100-yr
NE-T2-ST-3 Asbury Road 3.5' RCP Minor Arterial 50-yr with 1' GT 100-yr
overtop for
100-yr
Tributary No. 3
NF-T3-ST-1 NW Arterial 6' RCP Principal Arterial 100-yr with 0' GT 100-yr
overtop
NF-T3-ST-2 Embassy West 3- 3.5' RCP Residential 10-yr with no GT 100-yr
Drive 100-yr max.
overtop
Notes:
1. Hydraulic capacity at minimum roadway eIevafion.
2. CAP - concrete arch pipe, RCB-reinforced concrete box culvert, RCP - reinforced concrete pipe, CMP - corrugated metal
3. GT- Greater Than; LT - Less Than
4. Roadway classification based on City of Dubuque's skeet classification index.
3.4 PROBLEM AREAS
The flood hydrology and stream hydraulics models provide the results needed for identification
of areas that are not in compliance with the City's drainage standards/criteria. Problem areas in
the North Fork Drainage Basin range from flooding of residential structures to inadequate
conveyance systems. Figure 3-7 illustrates the locations of the identified problem areas. A
description of each of the identified problem areas is also presented in Table 3.6 and the
following section.
City of Dubuque, Iowa Drainage Basin Master Plan
North Fork Ca~sh Creek Drainage Basin 3-7 Fall 2001
NORTH FORK CATFI*SH CREEK DRATNAGE BASZN
Table 3.6
North Fork Catfish Creek Drainage Basin
Identified Problem Area Summary
Main Channel
NF-ST-4
J.F. Kennedy Road &
Pennsylvania Ave.
50-year flood event overtops for ultimate land use
conditions, but is contained within the street.
NF-ST-5 Keyway 10-year flood event overtops for ultimate land use
conditions. Four (4) structures are within the 100-year
flood level for ultimate runoff conditions.
NF-ST-6 Rosemont Street 10-year flood event overtops for ultimate land use
conditions. Eight (8) structures are within the 100-
year flood level for ultimate runoff conditions.
NF-ST-7 Northwest Arterial 50-year flood event overtops for ultimate land use
conditions.
NF-ST-9 Radford Road 50-year flood event overtops for ultimate land use
conditions.
NF-ST-10 Saratoga Road 10-year flood event overtops for ultimate land use
conditions.
Tributary No. 2
NF-T2-ST-1
50-year flood event overtops for ultimate land use
conditions.
Hillcrest Road
Asbury Rd
NF-T2-ST-2 50-year flood event overtops for ultimate land use
conditions.
Special Problem Area
Hillcrest Road &
Rosemont Street
100-year flood event overtops for existing land use
conditions.
The J.F. Kennedy Road & Pennsylvania Ave. (NF-ST-4) culvert is overtopped during flood
events exceeding the 50-year event. The flooding is restricted to the street; therefore, no action
is required.
The main channel and the drainage structures from the Northwest Arterial to Keyway cause
structural damages and are overtopped during flood events with less than a 10-year return period.
The drainage improvements for this reach are discussed in a subsequent section.
Saratoga Road (NF-ST-10) crosses the North Fork with a 30-inch RCP/36-inch RCP. Ultimate
development conditions are projected to increase the peak flow at this site such that the 10-year
flood event will overtop the roadway. Improvements recommended to upgrade Saratoga Road to
pass a 10-year flood event include enlarging the existing culvert by adding a 36-inch RCP.
City of Dubuque, Iowa Drainage Basin Master Plan
North Fork Catfish Creek Drainage Basin 3-8 Fall 2001
NORTH FORK CATFISH CREEK DRAINAGE BASIN
However, these improvements are within the City of Asbury's jurisdiction, so the City of
Dubuque would not be directly responsible for the estimated $21,000 required for the proposed
improvement.
The Hillcrest Road structure (NF-T2-ST-1) crosses Tributary No. 2 between St. Celia Street and
Winnie Court. Two (2) options are recommended which includes either detention storage or
drainage structure improvements. The 100-year peak discharge is nearly 800 cfs and the total
runoff volume is 96 acre-feet for the existing land use condition (agricultural). To contain the
peak storm volume, the detention volume behind Hillcrest Road must be increased from an
existing storage volume of 7 acre-feet to 16.3 acre-feet to eliminate roadway overtopping at
Itillcrest Road. The estimated cost for a detention proposed improvement is $76,000. If
detention is not viable, the culvert must be increased from an 84-inch RCP to a 108-inch RCP in
order to pass the existing peak flow without roadway overtopping. The estimated cost for the
proposed drainage structure improvement is $100,000.
The Asbury Road structure (NF-T2-ST-2) crosses Tributary No. 2 between Northwest Arterial
and St. Celia Street. Ultimate development conditions are projected to cause minor overtopping
of the roadway for the 50-year flood event. Since the flooding is less than 0.3-foot, no proposed
improvements are required.
Another location where local flooding is a problem is at the intersection of Rosemont Street and
Hillcrest Road. Two (2) options are recommended which either includes detention storage or
drainage structure improvements. The peak 100-year runoff near Rosemont Street is
approximately 110 cfs and the total runoff volume is 12 acre-feet for the existing land use
condition (agricultural). In order to contain the entire volume of the storm and eliminate
roadway overtopping at Hillcrest, a 12 acre-feet detention pond is required. The estimated cost
for a detention proposed improvement is $23,000. If detention is not viable, it is recommended
to construct a 42-inch storm sewer to convey the peak discharge downstream and to eliminate
roadway overtopping at Hillcrest. The estimated cost for the proposed storm sewer improvement
is $90,000.
3.5 DEVELOPMENT OF ALTERNATIVE SOLUTIONS
3.5.1 Detention
Detention offers a means of controlling major flood events to prevent damage to downstream
properties and infrastructure. Detention basins function by impounding runoff from an upstream
basin and releasing it at a controlled rate to minimize downstream flooding. Table 3.7 presents a
summary of the detention basins congidered in this study. Figures 3-8 and 3-9 show a potential
layout configuration for the Northwest Arterial and Pennsylvania Avenue detention storage sites.
City of Dubuque, Iowa Drainage Basin Master Plan
North Fork Ca~fish Creek Drainage Basin $-9 Fall 2001
NORTH FORK CATFI'SH CREEK DRAI'NAGE BASIN
Located along the northern branch of North Fork upstream of the Northwest Arterial is an
existing storage area. A 6-foot RCP conveys the water downstream. The inlet structure has been
modified to encourage upstream storage and regxtlate the downstream flow. The existing storage
volume is approximately 52 acre-feet at the top of the road elevation or elevation 838. The
maximum depth of water was computed at 19 feet. Prior to roadway overtopping, the residential
lawns located along the right bank or southern bank flood.
Additional storage upstream of the Northwest Arterial can be achieved by excavating
approximately 12-feet from the maintained lawns or from elevation 836 to elevation 821 at a
3H:IV slope. This would increase the storage to 110 acre-feet and require the excavation of
approximately 95,500 cubic yards of material. A two-staged inlet would be constructed to create
a detention cell.
Upstream of Pennsylvania, along the North Fork, is another opportunity to increase storage.
Between Keyway and Pennsylvania, along the main channel, the area is heavily wooded and
storage is available. Additional storage can be obtained through excavation. Excavation was
limited to 4-feet because soil boring logs conducted for a private developer showed bedrock
within 6-feet of the surface. Excavation of 35,000 cubic yards of material would increase
storage from 40 acre-feet to 62 acre-feet or excavation of 70,000 cubic yards of material would
increase storage from 40 acre-feet to 87 acre-feet.
City of Dubuque, Iowa Drainage Basin Master Plan
North Fork Catfish Creek Drainage Basin $-10 Fall 2001
NORTH FORK CATFISH CREEK DRATNAGE BASIN
3.5.2 Channel and Drainage Structure Tmprovements
3.5.2.1 Upstream of University Avenue
The segment of North Fork between Northwest Arterial and University Avenue was identified as
a problem area. Numerous structures are located within the 100-year floodplain and are
relatively low in relation to the creek and likely incur frequent flooding. Major channel
improvements would be required to lower the 100-year level below the floor elevation of the
structures. It is proposed to improve the creek channel by cleating, shaping and/or increasing the
capacity of several drainage structures.
A HEC-RAS hydraulic model was developed to describe the hydraulic conditions of the channel
and drainage structures between Northwest Arterial and University Avenue· The peak
discharges generated from the I-IEC-HMS model were used. Three (3) alternatives were
evaluated. Alternative No. 1 proposes to increase the storage upstream of Pennsylvania Avenue,
while Alternative No. 2 proposes to increase the storage upstream of the Northwest Arterial and
Alternative No. 3 proposes to increase the storage upstream of both Pennsylvania Avenue and
Northwest Arterial.
A baseline HEC-RAS model with current channel geometry was used to compare with proposed
improvements. Cross-sections were based on data obtained from the digital terrain model
(DTM) provided by the City. The channel geometry was assumed to be adequate for this study;
however, surveyed channel inverts may be lower than those shown in the model.
Rosemont Street, Keyway, and Pennsylvania Avenue cross the main channel. The existing
culverts and roadway geometry were modeled based on both DTM and survey information. A
single 72-inch reinforced concrete pipe (RCP) culvert, twin 78-inch RCP culverts, and a single
14.5-foot corrugated metal pipe are located at the Rosemont Street, Keyway, and Pennsylvania
Avenue crossings, respectively.
Manning's coefficients and entrance loss coefficients for the culverts were estimated based on
site visits and guidelines presented in the HEC-RAS User's Manual. Manning's coefficients of
0.011 and 0.028 were used for concrete and corrugated metal, respectively. An entrance loss
coefficient of 0.5 was used at Rosemont Street and Keyway while 0.7 was used at Pennsylvania
Avenue because of the inlet configuration.
Manning's coefficients for the channel and overbanks were based on guidelines in "Open
Channel Hydraulics," by Chow. A value of 0.035 was used for the channel upstream of Keyway,
while a higher value of 0.040 was used downstream where the channel is mom congested with
Ci~ of Dubuque, Iowa Drainage Basin Master Plan
North Fork CaOSsh Creek Drainage Basin 3-12 Fall 2001
NORTH FORK CATFI'SH CREEK DRAi'NAGE BASI'N
trees. Overbank Manning's values ranged from 0.050 to 0.10 representing conditions ranging
from grassy areas with few trees to heavy stands of timber.
The baseline hydraulic model showed all three roadways to be overtopped during 100-year flood
discharges. In addition, several yards and homes were affected by flooding. Proposed condition
models were created to determine measures to significantly reduce or prevent damage to private
property and infrastructure caused by 100-year flood flows. Improvement options studied
included channel clearing, channel shaping, and/or drainage structure improvements. Manning's
coefficients were decreased in some locations to represent channel clearing; a minimum value of
0.035 was assumed. Channel shaping was accomplished with the channel modification option in
HEC-RAS. Channel geometry was modified to create a trapezoidal shape with 3H:IV side
slopes. The bottom width of the channel was changed to accommodate larger culverts or to
increase channel conveyance; thereby, reducing water surface elevations. The channel
downstream of Pennsylvania Avenue was not reshaped for the proposed conditions; however, the
roughness was decreased to reflect channel clearing.
An improved entrance loss coefficient of 0.2 was used for all culverts. Culverts were replaced or
supplemented to decrease or prevent a depth of flow over the roadways. A maximum depth over
the roadways of 0.5 feet was used as the criteria for this analysis.
Table 3.8 presents a summary of the channel and drainage structure improvements and an
estimated capital cost within the North Fork Drainage Basin. Figures 3-10, 3-11, 3-12 and 3-13
note the proposed channel and structural improvements between Northwest Arterial and
University Avenue.
It is proposed to improve the existing entrance of the 14.5-foot corrugated metal pipe at the
intersection of Pennsylvania Avenue and J.F. Kennedy Road by reestablishing the embankment
around the pipe and installing rock riprap and a concrete collar around the pipe. In addition, a
portion of the upstream channel would be realigned and a 310-foot long structural concrete wall
built at the top of the slope above the inlet. The concrete wall would be 3-feet high, allowing an
additional 2 feet of ponding with 1 foot of freeboard (top of wall elevation approximately 783
feet). The ponding elevation is limited because storm sewer inlets along Pennsylvania Avenue
and J.F. Kennedy Road would begin to allow water to flow into the road from the culvert should
the water surface upstream become too high. Alternative No. 3 requires the 14.5-foot opening be
restricted to a 10-foot opening by constructing a concrete inlet that blocks the opening. The 10-
foot opening does not cause any backwater effects on Keyway and provides 1.5-foot of freeboard
on the structural wall.
The proposed improvements described above drastically reduce flooding limits on the study
reach. For the Alternative No. 2 flow condition, roadway overtopping has been eliminated at
Rosemont Street and Keyway and backyard flooding is reduced to the channel upstream of
City of Dubuque, Iowa Drainage Basin Master Plan
North Fork Catfish Creek Drainage Basin 3-13 Fall 2001
NORTH FORK CATFISH CREEK DRAINAGE BASIN
Keyway. For the Alternative No. 1 flow condition, roadway overtopping has also been
eliminated and flooding is generally kept away from structures upstream of Keyway, although
several entire back yards remain inundated.
3.5.2.2 Downstream of University Avenue
An apartment complex and one (1) home immediately downstream of the Pennsylvania Ave.
culvert would still experience flooding with the improvements in place. A field investigation
was performed and it was found that the first floor elevation of the apartments located closest to
the channel was 767.5 and that the apartment building is constructed on piles without a
basement. The existing 100-year water surface elevation was determined to be at elevation
765.5; therefore, the storm water affects the substructure of the apartments, but the first habitable
floor is dry. The 100-year water surface elevation of Alternative No. 3 was 764.6, thereby
reducing the 100-year water surface elevation less than 1-foot. The reduction in flooding of
Alternative No. 3 quickly dissipates downstream of Pennsylvania Avenue/J.F. Kennedy Road
and the associated costs quickly exceed the resulting benefit of the proposed alternatives.
There have been complaints of frequent flooding of agricultural ground in the reach immediately
upstream of University Avenue. To investigate flooding problems in this area, the existing
conditions hydraulic model described above was extended downstream to include University
Avenue, U.S. Highway 20, and the reach immediately downstream of U.S. Highway 20. Under
existing conditions, a 12-foot by 12-foot reinforced concrete box approximately 280 feet in
length passes under University Avenue and a 26.5-foot by 18.5-foot arched concrete culvert
passes under U.S. Highway 20. A normal depth boundary condition was used for this model.
Using this extended model, the installation of an additional structure at University was analyzed.
With the existing model as a baseline, the effect of constructing an additionall2-foot by 12-foot
RCB culvert was investigated. Based on the model results, the additional structure would
produce a maximum decrease in water surface elevation of 5.5 feet and reduce the inundated area
by approximately 3.5 acres. An estimate of the cost required to construct an additional 12-foot
by 12-foot RCB beneath University Ave. is included in the Opinion of Probable Construction
Costs Appendix. Given the high cost of construction and the relatively small impact to the
inundated agricultural ground adjacent to the stream, it is not recommended to add an additional
structure.
City of Dubuque, lowa Drainage Basin Master Plan
North Fork Ca~ish Creek Drainage Basin 3-]5 Fall 200]
NORTH FORK CATFISH CREEK DRAINAGE BASIN
3.5.3 Flood Inundation
Figures 3-14, 3-15, 3-16, and 3-17 depict the 100-year existing, Alternative No. l, and
Alternative No. 2 flood inundation. These figures show the approximate limits of flooding. The
flood inundation for Alternative No. 3 is similar to Alternatives Nos. 1 and 2 and was not shown
on the flood inundation figures.
3.6 RECOMMENDATIONS FOR IMPROVEMENT ALTERNATIVES
The program developed for the City consists of the recommended solutions for the North Fork
Drainage Area. These recommended solutions are located within the city limits and could be
implemented by the City. The peak discharges associated with all three North Fork Drainage
Basin alternatives are summarized in Table 3.9.
Table 3.9
North Fork Catfish Creek Drainage Basin
Peak Runoff Summary for Existing and Proposed Hydraulic Conditions
Main Channel
NF-ST- t 26 Bmnskill Rd. 3.8 3,130 3,120 3,120 3,100
NF-ST-2 22 US 20 3.2 2,490 2,430 2,460 2,270
(Dodge St.)
Highway
NF-ST-3 49 University 3.0 2,420 2,370 2,390 2,070
Avenue
NF-ST~ t8 J.F. Kennedy 2.1 2,080 2,080 2,1M0 1,830
Rd. &
Pennsylvania
Ave.
NF-ST-5 9 Keyway 1.7 2,280 2,500 2,160 2,160
NF-ST-6 35 Rosemont St. 0.94 1,070 1,320 950 950
NF-ST-7 10 Northwest 0.52 650 590 180 180
Arterial
NF-ST-8 36 Sunnyslope 0.26 770 770 770 770
NF-ST-9 3 Radford Rd. 0.16 470 470 470 470
NF-ST-10 5 Saratoga Rd. 0.06 160 160 160 160
City of Dubuque, Iowa Drainage Basin Master Plan
North Fork Catfish Creek Drainage Basin 3-16 Fall 2001
NORTH FORK CATFI'SH CREEK DRAI'NAGE BASI'N
Table 3.9
North Fork Catfish Creek Drainage Basin
Peak Runoff Summary for Existing and Proposed Hydraulic Conditions
Tribut_~. No. 1
NF-T1-ST-t 57 Bnmskill Rd 0.41 850 850 850 850
NF-T1-ST-2 54 US 20 0.14 320 320 320 320
(Dodge St.)
Tributary. No. 2
NF-T2-ST- 1 33 Hillcrest Rd. 0.41 800 800 800 800
NF-T2-ST-2 30 Asbury Road 0.15 360 360 360 360
NF-T2-ST-3 29 Asbury Rd. 0.03 60 60 60 60
Tributary No. 3
NF-T3-ST- 1 12 NW Ar~eriai- 0.2t 460 460 460
NF-T3-ST-2 13 Embassy 0. t0 210 210 210
West Dr.
Notes:
Peak rmaoff rates based on ultimate land use conditions and simulation of a 24-hour storm event.
2. See Figure 3-1 for location of structure identification number.
3. See Figure 3-6 for location of HEC-HMS node and identification number.
4. Peak discharges reported are outflows from the specified nodes.
5.
460
210
Altemadve No. 1 - Build additional detention storage at Pennsylvanitc Build charmel improvements from Northwest
Arterial to approximately 530 feet downstream of Keyway. Improve outlet at Northwest Arterial.
Alternative No. 2 - Build additional detention storage at Northwest Arterial. Build channel improvements from Northwest
Arterial to approximately 530 feet downstream of Keyway.
Alternative No. 3 - Build additional detention storage at Pennsylvania Avenue and Northwest Arterial. Build channel
improvements from Northwest Arterial to approximately 530 feet downstream of Keyway.
It is recommended to construct Alternative No. 2 and expand the existing storage upstream of the
Northwest Arterial. This area aids in reducing the peak discharges downstream and provide a
water quality benefit as the sediment-laden water is provided an opportunity to settle-out. While
this alternative is not the least cost alternative, the additional incremental impact on flooding is
substantial relative to the increased cost. Additionally, it is more aesthetically desirable, as it
does not require destruction of the heavily wooded area upstream of Pennsylvania Avenue. It is
also recommended to obtain 100-year flowage easements on private property and purchase flood
prone properties as they become available. Commercial development opportunities exist along
the left overbank, parallel to J.F. Kennedy Road. It is recommended that any development
require a 2:1 excavation to flu ratio.
City of Dubuque, Iowa Drainage Basin Master Plan
North Fork Catfish Creek Drainage Basin 3-17 Fall 2001
NORTH FORK CATFI'SH CREEK DRAINAGE BASI'N
3.7 PRO3ECT PHAS'~NG
and recommended ~mprovements were ranked based on the resulting benefits
The problem areas costs of improYements in order to prioritize proposed improvements in the
in comparison to the
North Fork Drainage Basin. Table 3.10 presents a drainage basin priority based on other
proposed improvements within the drainage basin. It is recommended to conduct detention
improvements from the most upstream first and then proceed downstream. Channel
improvements are to be constructed from downstream to upstream.
Table 3.10
North Fork Catfish Creek Drainage Basin
Recommended Improvements Summary
1 (NF-ST-7)
2 ?ermsylvania (NF-ST4)
3 to Pennsylvania Reach
4 ~ (NF-ST-5)
5 Rosemont to Keyway Reach
Stxeet & Ylillarest
7 Road (Special Problem Area) __
to Rosemont
8
Street Reach __
9 Hillcrest Road (NF-T2-ST-1)
-- Excavate upstream detention and build two- $587,300
: outlet structure.
-- Build concrete structural wall. Improve inlet. $157,400
Trap. channel with bw of 25'and side slopes of $122,500
3H:IV.
slxucture and build 3 - 10'x $331,800
$293,000
8' RCBs or 240 S
-- Rosemont to Ellen: trap. channel with bw of
10', side slopes of 3H:IV; Ellen to Keyway:
trap. channel with b,~ of 25' and side slopes of
3H: IV.
additional 72" RCP or 57 SF of total
$61,800
12 AF of storage ($23,000) or
Build 42" storm sewer ($90,000)
Trap. channel with bw of 10' and side slopes
:IV.
Provide 16.3 AF of storage ($76,000) or
· 08"
Remove existing stxucmre and budd 1
RCP ($110,000)
$20,200
Saratoga Road (NF-ST- 10)
1 additional 3' RCP.
$21,000
Estimated capital costS include contingencies (25%) to account fo~ estimated quanUt~es, umt puce adjustmentS and imscella~eous work
Aa additional 25% was included for adminislxative, legal mad engineenng costs. Right-of-way, opexaUOn and mamtertance
Drainage Basin Master Plan
Fall 2001
City of Dubuque, Iowa 3-18
North Fork Catfish Creek Drainage Basin
NORTH FORK CATFISH CREEK DRAINAGE BASi'N
3.7 PROJECT PHASING
The problem areas and recommended improvements were ranked based on the resulting benefits
in comparison to the costs of improvements in order to prioritize proposed improvements in the
North Fork Drainage Basin. Table 3.10 presents a drainage basin priority based on other
proposed improvements within the drainage basin. It is recommended to conduct detention
improvements from the most upstream first and then proceed downstream. Channel
improvements are to be constructed from downstream to upstream.
Table 3.10
North Fork Catfish Creek Drainage Basin
Recommended Improvements Summary
1 Northwest Arterial (NF-ST-7) Excavate upstream detention and build two- $587,300
stage outlet structure.
2 Pennsylvania (NF-ST-4) Build concrete structural wall. Improve inlet. $157,400
3 Keyway to Pennsylvania Reach Trap. channel with b,~ of 25'and side slopes of $122,500
(approx. 530') 3H:iV.
4 Keyway (NF-ST-5) Remove existing structure and build 3 - 10'x $331,800
V RCBs or 240 SF of total opening required
5 Rosemont to Keyway Reach Rosemont to Ellen: trap. channel with bw of $293,000
10', side slopes of 3H:IV; Ellen to Keyway:
trap. channel with bw of 25 and s~de slopes o
3H: 1V.
6 >,osemont Street (N~_-ST-6) Build 1 additional 72" RCP or 57 SF of total $61,800
opening required.
7 Rosemont Street & Hillerest Provide 12 AF of storage ($23,000) or $23,0003
Road (Special Problem Area) Build 42" storm sewer ($90,000)
8 Northwest Arterial to Rosemont Trap. channel with bw of 10' and side slopes $20,200
Street Reach of 3H: iV.
9 Hillcrest Road CNF-T2-ST-I) Provide 16.3 AF of storage ($76,000) or $76,0003
Remove existing structure and build 108"
RCP ($110,000)
[ Saratoga Road (NF-ST-10) I Build 1 additional 3' RCP. $21,000
I
(Asbury Jurisdiction)2
I
and mitigation costs were not included. Costs based on Iowa Department of Transportation 1999 unit prices.
2. The Saratoga Road (NF-ST- 10) impr°vements are within the jurisdiction °f the City °f Asbttry; ~°re' the i~r°vem~t c~t w~ u°t
included with the other dntinage basin improvements.
City of Dubuque, Iowa Drainage Basin Master Plan
North Fork Catfish Creek Drainage Basin 3-18 Fall 2001
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BEE BRANCH DRAINAGE BASIN
4.0 BEE BRANCH DRAINAGE BASI'N
4.1 GENERAL DRA~*NAGE BASTN DESCR/PTi'ON
The Bee Branch Drainage Basin (Bee Branch) is located in the central vicinity of the Dubuque
municipal limits and is shown on Figure 4-1. The drainage basin measures approximately 7.1
square miles, and flows in a southeasterly direction to the 16th Street Detention Cell and
discharges into the Mississippi River through a 12-foot by 12-foot RCB equipped with dual
sluice gates. The main Bee Branch channel is primarily located along West 32nd Street and
Washington Street. The drainage area is roughly bounded by West 32nd Street to the north,
Asbury Road and University Avenue to the south, Northwest Arterial to the west and the
Mississippi River to the east.
The basin consists of several large subareas draining from large bluffs into a fiat, densely
populated lowland area within the old Mississippi River floodplain, hereafter referred to as the
Couler Valley area. The subareas include West 32nd Street, Kaufmann Avenue, Locust Street,
Washington Street (main Bee Branch trunk line storm sewer), Windsor, 1 lth Street, 14th Street,
Upper Kerper and Lower Kerper. During flood events on the Mississippi River, runoff is
diverted from Dock Street (at elevation 600.5 or stage 15) and Hamilton Street (at elevation
603.5 or stage 18) subareas through a 60-inch RCP located between Hamilton Street and Dock
Street and a 78-inch RCP between Dock Street and a ditch south to Fengler Street. At elevation
598.5 or stage 13, the 8th Street Subarea is diverted into the 16th Street Detention Cell. Table
4.1 displays the drainage area for each subarea of the Bee Branch Drainage Basin.
City of Dubuque, lowa Drainage Basin Master Plan
Bee Branch Drainage Basin 4-] Fall 2001
BEE BRANCH DRAi'NAGE BASI'N
Table 4.1
Bee Branch Drainage Basin
Drainage Areas for Subareas
West 32nd Street 1.90
Kaufmann Avenue 1.31
Locust Street 0.90
Windsor Avenue 0.39
Washington Street 1.15
Hamilton Street 0.16
Dock Street 0.16
Upper Kerper 0.28
Lower Kerper 0.09
14th Street 0.16
1 lth Street 0.21
8th Street 0.41
Total Bee Branch Drainage Basin Area: 7.12
The Bee Branch Drainage Basin is relatively steep, with an average terrain slope of
approximately 37 percent. The overall slope of the main channel in the upland areas is
approximately 2 percent, while the slope of the main channel in the flat Couler Valley area to the
outlet is approximately 0.5 percent. Elevations in the drainage basin range from 594 feet NGVD
at the 16th Street Detention Cell at the Mississippi River to 962 feet NGVD in the upper reaches
of the drainage basin. Figure 4-2 shows the range of slopes for the Bee Branch Drainage Basin.
Information on the soil types and characteristics in the Bee Branch Drainage Basin was compiled
by developing a digital soils database in GIS. Table 4.2 shows the relative representation and
general hydrologic characteristics for the different soil series found in the Bee Branch Drainage
Basin. The Bee Branch Drainage Basin consists of over 19 different soil types, of which the
Fayette-Urban Land Complex and the Fayette Silt Loaxn series account for over 40 percent of the
total drainage basin area. For modeling purposes, the different soil types were grouped by the
NRCS hydrologic soil type as Type A, B, C, or D. Nearly the entire drainage basin consists of
Type B soils, as depicted in Figure 4-3.
City of Dubuclue, lowa Drainage Basin Master Plan
Bee Branch Drainage Basin 4-2 Fall 2001
BEE BRANCH DRAt'NAGE BAS 'N
Table 4.2
Bee Branch Drainage Basin
Soil Type Summary
Fayette-Urban Land (5 to 20% slopes) Moderately to strongly Silt Loam 39 27.3
Complex (4163C1, sloping, well-drained soil and urban land
4163D1, 4163E1) on side slopes in uplands within the City
of Dubuque. Moderate permeability with
medium to rapid runoff.
Fayette Silt Loam (5 to 25% slopes) Moderately to Silt Loam 65 14.4
(163C1, 163C2, strongly sloping, well drained soil on
163D1, 163D2, side slopes in uplands. Moderate
163E1, 163E2, permeability with medium to rapid
163F1, 163F2) runoff.
Nordness Rock (18 to 60% slopes) Steep and very steep, Sik Loam 8 14.1
Outcrop Complex well drained soils and rock outcrop on
(478G) convex side slopes and escarpments.
Moderate permeability with rapid runoff.
Psamments-Urban (0 to 2% slopes) Areas where material Variable - 1 7.9
Land (5070) dredged from the Mississippi River has Typically
been deposited. Rapid to very rapid Coarse
permeability with slow runoff. Sand
Urban Land- (2 to 5% slopes) Gently sloping areas of Silt Loam 1 7.7
Dorchester Complex urban land with well drained Dorchester
(4158B) soil on wide bottomlands and along
narrow drainage ways within the City of
Dubuque. 'Moderate permeability with
slow runoff.
Urban Land-Lamont (2 to 7% slopes) Gently sloping to Fine 2 6.4
Complex (4110B) moderately sloping areas of urban land Sandy
with well-drained Lamont soil located on Loam
I ridges and side slopes on high stream
terraces within the City of Dubuque.
Moderately rapid permeability with
medium rtmoff.
Dorchester-Volney (2 to 5 % slopes) Gently sloping, 4 4.1
Complex (496B) moderately well-drained to well-drained
soils on alluvial fans and in the lower
part of narrow drainageways.
Various soils. 12 soil types ranging from 131 18.1
0.08% to 3.3% area.
Total Percent Area 100.0 %
Sottrce: Soil Survey of Dubuque County, Iowa; SCS, December 1985.
City of Dubuque, Iowa Drainage Basin Master Plan
Bee Branch Drainage Basin 4-3 Fall 2001
BEE BRANCH DRAI'NAGE BASI'N
The drainage system in the Bee Branch Drainage Basin consists of both natural channel and
closed conduit sections. The majority of the drainage basin is highly developed and therefore
much of the runoff is conveyed through storm sewer systems. Generally, natural channels are
only present in less densely populated upland areas, specifically the West 32nd Street Subarea.
A land use database containing information for ultimate development was created based on the
City's 1999 GIS Comprehensive Land Use Plan and supplemented with land use projections
made by City staff. Land use classifications in Bee Branch range from open spaces to industrial,
with the majority of the drainage basin being classified as low density and medium density
residential and commercial land uses. The breakdown of land use within the Bee Branch
Drainage Basin for ultimate development is shown in Table 4.3 and Figure 44.
Table 4.3
Bee Branch Drainage Basin
Land Use Summary
Streets 437 9.6
Industrial 195 4.3
Commercial 289 6.3
Institutional 624 13.7
High Density Residential 239 5.3
Medium Density Residential 1,377 30.2
Low Density Residential 205 4.5
Agricultural 146 3.2
Open Space and Grass 1,045 22.9
Total 4,557 100.0%
Source: City of Dubuque, Iowa Comprehensive Land Use Plan, 1999.
Note: Water bodies are inco~:~orated into adjacent parcel land use categories.
While local flooding problems exist in the upland areas of the basin, the primary flooding
problem in the Bee Branch occurs in the heavily developed Couler Valley area located in the
former Mississippi River floodplain. While this area is protected from high Mississippi River
stages by levees, flooding problems persist due to interior drainage. During large storm events,
runoff from the steep upland areas rapidly drains toward the Couler Valley area. The flat
topography of the Couler Valley area and the system of levees then slow the progression of the
floodwaters to the Mississippi River. Additionally, existing storm sewer systems intended to
collect and convey flood flows do not have the capacity to provide significant relief during
extreme events. These problems combine to make the Couler Valley area of Dubuque prone to
serious flooding during large storm events. Figure 4-5 depicts flooding from the main storm
City of Dubuque, Iowa Drainage Basin Master Plan
Bee Branch Drainage Basin 4-4 Fall 2001
BEE BRANCH DRAINAGE BASIN
sewer trunk line of the Bee Branch for a 100-year 24-hour rainfall event and is an indication of
the severity of the problem.
Few flood control measures have been implemented in the Bee Branch Drainage Basin, other
than several regional detention cells on the main channel. The Bee Branch Drainage Basin is
one of the few drainage basins in which regional detention of storm runoff is used and expanding
existing detention cells may be a viable alternative for flood control.
Regional detention is most effective when applied in the upper portions of the drainage basin.
Natural detention upstream of several drainage structures offers an opportunity to reduce the
peak discharges and water surface elevations downstream. As the drainage basin becomes more
developed, the number of available detention sites is reduced and detention options are
eliminated or limited to expansion of existing detention cells. Regional detention sites were
analyzed along with channel improvements that can be implemented as a potential means of
flood control in the Bee Branch Drainage Basin.
Conveyance alternatives may also be a viable alternative for flood control in the lower roaches of
Bee Branch. The topography of the lower reaches of Bee Branch does not provide any viable
alternatives for detention sites, so increasing conveyance becomes the primary mechanism for
minimizing flood impacts. Increasing the hydraulic capacity of the storm sewer system through
resizing or adding relief sewers may reduce flooding impacts for smaller flood events.
The following sections describe each of the five (5) drainage subareas of the Bee Branch. The
improvement alternative discussed is limited to the specific subarea. For this study, the main
Bee Branch channel improvements along West 32nd Street are described within the West 32nd
Street Subarea and the Bee Branch storm sewer trunk line sections.
4.2 WEST 32ND STREET DRAINAGE SUBAREA
4.2.1 General Subarea Description
The West 32nd Street Drainage Subarea is located in the upper reaches of the Bee Branch
Drainage Basin. The drainage subarea measures approximately 1.9 square miles and drains into
the West 32nd Street Detention Cell and then discharges into the Bee Branch storm sewer trunk
line through a 10-foot x 9-foot concrete arch pipe. The drainage area is roughly bounded by
West 32nd Street to the north, Asbury Road, Carter Road and Kane Street to the south,
Northwest Arterial to the west, and Wildwood Drive to the east.
City of Dubuque, Iowa Drainage Basin Master Plan
Bee Branch Drainage Basin 4-5 Fall 2001
BEE BRANCH DRAI'NAGE BASI'N
4.2.2 Flood Hydrology
The HEC-HMS model was utilized to compute the peak runoff rates for the 10-year, 50-year,
100-year and 500-year return period storm events. Runoff hydrographs were developed for each
storm event for ultimate development conditions, as defined by the City's comprehensive land
use plan. Figure 4-6 depicts the subbasin delineation, while Figure 4-7 is a schematic of the
HEC-HMS model.
Table 4.4 provides a summary of peak runoff rates for selected storm events at key locations in
the West 32nd Street Drainage Subarea. A summary of the peak runoff rates for all subbasin
hydrographs can be found in the Hydrologic and Hydraulic Appendices.
Table 4.4
West 32nd Street Drainage Subarea Peak Runoff Summary
Existing Drainage System Conditions
West 32nd - Main Channel
W32-ST-1 4 West 32nd St. 1.9 860 1,750 2,140 3,300
Detention
Cell4
W32-ST-2 3 Fink St. 1.8 1,120 1,770 2,140 3,290
W32-ST-5 10 West 32nd St. 1.8 1,120 1,770 2,140 3,280
W32-ST-6 2 Wildwood Dr. 1.7 1,100 1,730 2,100 3,220
W32-ST-9 1 Grandview 1.6 1,080 1,700 2,050 3,140
Ave.
W32-ST-12 14 Carter Road 1.0 850 1,290 1,540 2,430
W32-ST-13 7 Pedestrian 0.38 360 460 560 1,160
Bridge
W32-ST-14 21 J.F. Kennedy 0.30 310 400 630 1,070
Road
W32-ST-15 18 Northwest 0.05 30 60 70 110
Arterial
West 32nd Street - Tributary, No. 1
W32-T1-ST~l 90 Carter Road 0.19 160 260 320 500
W32-T1-ST-3 12 Kerry Ct. 0.15 130 210 270 410
, W32-T1-ST-4 12 Killarney Ct. 0.15 130 210 270 410
1. See Figure 4-6 for location of structure identification number.
2. See Figure 4-7 for location of HEC-HMS node and identification number.
3. Peak ranoff rates based on ultimate land use conditions and simulation of a 24-hour storm event.
4. Peak discharges reported are outflows ii:om the specified node.
5. Peak runoff rates for West 32nd Detention Cell represent peak outflows from the stmctm-e, not inflows into the detention
cell.
City of Dabuque, Iowa Drainage Basin Master Plan
Bee Branch Drainage Basin 4-6 Fall 2001
BEE BRANCH DRAINAGE BASIN
4.2.3 Stream Hydraulics
HEC-HMS was used to determine the depth of overtopping for the drainage structures analyzed
in the main channel and tributaries. At design points where a stage-storage-discharge
relationship was analyzed by HEC-HMS, the peak stage was compared to the minimum
overtopping elevation. At design points where the storage was negligible, an independent stage-
discharge relationship was established using the inlet control nomograph from HDS-5. Weir
flow and pipe flow were combined to find a peak stage, and this peak stage was then compared
to the minimum overtopping elevation. A total of twelve road crossings were analyzed in the
West 32nd Street Drainage Subarea. A surnmary of the hydraulic capacity for each of the
crossings studied is presented in Table 4.5 for the 10-, 50-, and 100-year storm events.
Table 4.5
West 32nd Street Drainage Subarea
Existing Hydraulic Capacity of Stream Crossings Summary
Main Channel
W32-ST-1 West 32nd Street 644.0 0.0
Detention Cell4
W32-ST-2 Fink Street 648.2 0.04
W32-ST-5
West 32nd Street
660.43
0.6
W32-ST-6 Wildwood Drive 662.9 0.3
W32-ST-9 Grandview Avenue 672.7 0.0
W32-ST-12 Carter Road 719.0 0.8
W32-ST-13 Pedestrian Bridge 796.3 0.0
W32-ST-14 J.F. Kennedy Road 820 0.0
W32-ST-15 Northwest Arterial 925.2 0.0
1.4 1.7
0.¢ 0.¢
1.1 1.4
1.1 1.4
0.8 1.1
1.5 1.8
0.0 0.0
0.0 0.7
0.0 0.0
Tributary No. 1
W32'T1-ST-1 I CarterRoad 710.33 0.0 0.0 0.0
W32-T1-ST-3I Kerry Court 787.33 0.0 0.4 0.6
W32-T1-ST4 Killarney Court 810.53 0.6 0.9 1.2
Notes:
1. Depth of overtopping obtained from HEC-HMS analysis, tmless otherwise noted.
2. Minimum overtopping elevation based on topographic survey, unless otherwise noted.
3. Mirdmum overtopphig eleva~on based on minimum roadway elevation obta/ned by interpolating City, s DAGiS mapping.
4. Assumes reconstructed outlet stmctm-e. See stage-storage-discharge relationship in Hydrologic and Hydraulic Appendices.
The drainage standards/criteria of passing the design flood event without roadway overtopping
was evaluated for each crossing. A summary of the return period for each of the crossings
studied is presented in Table 4.6.
City of Dubuque, Iowa Drainage Basin Master Plan
Bee Branch Drainage Basin 4-7 Fall 2001
BEE BRANCH DRAI'NAGE BASTN
Table 4.6
West 32nd Street Drainage Subarea
Existing Hydraulic Capacity and Return Period of Stream Crossings Summary
West 32nd Street -Main Channel
Minor 50-yr with 1' 1.4' overtop for
W32-ST-I West 32nd St. @ Earthen Berm w/ Arterial overtop for 50-yr & 1.7' for
Detention Cella Concrete Riser
lO0-yr lO0-yr
I Residential lO~yr with no GT 100-yr4
W32-ST-2 Fink St. : 22' x 11' RCB 100-yr max.
overtop
Minor 50-yr with 1' 0.6' overtop for
W32-ST-5 West 32nd St. 9.8' x 7.7' RCB Arterial overtop for 10-yr & 1.1' for
100-yr 50-yr
Residential I0-yr with no 0.3' overtop for
W32-ST-6 Wildwood Dr. 2 - 10' x 6.3' RCB 100-yr max. 10-yr & 1.1' for
overtop 50-yr
Minor 50-yr with 1' 0.8' overtop for
W32-ST-9 Grandview Ave. 2 - 10.5' x 7'
RCAP Arterial overtop for 50-yr & 1.1' for
I00-yr 100-yr
Collector 50-yr with 0.8' overtop for
W32-ST-12 Carter Road 2 - 7' RCP 1.5' overtop 10-yr & 1.5' for
for 100-yr 50-yr
W32-ST-13 Pedestrian Bridge 7' RCP N/A GT 100-yr
W32-ST-14 J.F. Kennedy Rd. 5' CMP (in)/ Minor 50-yr with I' 50-yr with 0.7'
5'x 5.7' RCB (out) Arterial overtop for overtop for t00-
100-yr yr
W32-ST-15 Northwest Arterial 4' CMP (out)/ Principal Arterial 100-yr with GT 100-yr
4' RCP (in) 0' overtop
West 32nd Street - Tributary No. 1
Collector 50-yr with GT 100-yr
W32-T1-ST-I Carter Road 2- 5' RCP 1.5' overtop
for 100-yr
Residential 10-yr with no 0.0' overtop for
W32-Tt-ST-3 Kerry Court 4' CMP 100-yr max. 10-yr & 0.4' for
overtop 50-yr
Residential i0-yr with no 0.6' overtop for
W32-T1-ST-4 Killarney Court 3' RCP 100-yr max. 10-yr & 0.9' for
overtop 50-yr
Notes:
1. Hydraulic capacity at minimum roadway elevation.
2. RCB - reinforced concrete box culvert, RCAP - reinforced concrete arch pipe, RCP - reinforced concrete pipe, CMP -
corrugated metal pipe.
3. Roadway classification based on City of Dubuque's street classification index.
4. Assumes reconsm~cted outlet structure at West 32nd Street Detention Cell. Backwater impacts from West 32nd Street
Detention Cell are reflected at Fink Street.
City of Dubuque, Iowa Drainage Basin Master Plan
Bee Branch Drainage Basin 4-8 Fall 2001
BEE BRANCH DRAI'NAGE BASi'N
4.2.4 Problem Areas
The flood hydrology model provides the results needed for identification of areas that are not in
compliance with the City's drainage standards/criteria. Problem areas in the West 32nd Street
Drainage Subarea range from flooding of residential structures to inadequate drainage structures.
A description of each of the identified problem areas is presented in Table 4.7 and Figure 4-21
shows the location of the identified problem areas.
Table 4.7
West 32nd Street Drainage Subarea
Identified Problem Area Summary
Main Channel
W32-ST-1 West 32nd Street 50-year flood event overtops £or ultimate land use conditions
Detention Cell
W32-ST~5 West 32nd Street 50-year flood event overtops for ultimate land use conditions
W32-ST~6 Wildwood Drive 10-year flood event overtops for ultimate land use conditions
W32-ST-9 Grandview Ave. 50-year flood event overtops for ultimate land use conditions
W32-ST-12 Carter Road I 50-year flood event overtops for ultimate land use conditions
Tributar~ No. 1
W32-T1-ST-4 I Killarney Court I 10-year flood event overtops for ultimate land use conditions
Special Problem Area
Kaufmann Avenue
I City staff identified problem area
and
Martin
Drive
Notes:
1. Roadway classification based on City of Dubuque s~xeet classification index.
2. Criteria violations based on roadway overtopping design storms presented in Table 2.7.
Although few problems exist within the West 32nd Street Subarea, the subarea is a major
contributor to the flooding problems in the Couler Valley area. It is the largest of the upper
drainage subareas flowing toward the Couler Valley area, and the West 32nd Street Detention
Cell controls storm water runoff, thereby reducing the flooding downstream.
The six structures listed in Table 4.6 exceed the criteria presented in Table 2.7. The structures
are overtopped at their required design storm and several structures have overtopping depths for
the 100-year flood event in excess of the maximum allowable depth.
City of Dubuque, Iowa Drainage Basin Master Plan
Bee Branch Drainage Basin 4-9 Fall 2001
BEE BRANCH DRAINAGE BASIN
Special Study Area
A depressed area in the upper portion of the West 32nd Street Subarea also was investigated as a
problem area. The area is located along Kaufmann Avenue east of the Kaufmann/J.F. Kennedy
Road intersection. An existing storm sewer system adjacent to Kaufmann Avenue drains storm
water to a tributary north of Kaufmann Avenue near the Kaufmann and Martin Drive
intersection. The storm sewer trunk line was analyzed based on the assumption of full pipe flow
using peak discharges from the HEC-HMS hydrologic model of the subarea. The existing pipe
sizes were compared to the pipe sizes calculated to handle the 100-year peak discharge. It was
determined that the storm sewer system is undersized to meet a 100-year design standard. Based
on this analysis, the storm sewer along Kaufmann Avenue west of the Kaufmann/J.F. Kennedy
Road intersection should be replaced with a 60-inch RCP to handle the 100-year peak discharge.
The trunk line east of the Kaufmann/J.F. Kennedy intersection was shown to have capacity in
excess of the 100-year peak discharge. It was noted there were few storm sewer inlets located in
the depressed area. This should be investigated further to insure no flooding would occur due to
lack of inlet capacity in this location.
4.2.5 Development of Alternative Solutions
The West 32nd Street Subarea predominantly consists of well-drained uplands and therefore
contains few areas with flooding risks. Properties situated in the narrow valley of the Bee
Branch running adjacent to West 32nd Street are at risk due to their proximity to the stream and
their location in the lower portion of the subarea.
As mentioned previously, the West 32nd Street Subarea is a primary factor in the flooding
hazards encountered in the Couler Valley area; however, expansion of existing detention cells
and/or construction of additional storage areas in the West 32nd Street Subarea would reduce
peak discharges and retain large volumes of storm water runoff, potentially further reducing the
flooding problems downstream. Construction of storage areas in the upland portions of the
subarea would have an impact on the flood damages experienced, not only in the Couler Valley
but also, in the low lying areas of the West 32nd Street Subarea.
Channel improvements would have limited benefit because they would impact only a small
number of properties located adjacent to the well-defined stream in the lower portion of the
subarea. Flood proofing or property buyout would be a more effective alternative to address
chronic flooding problems. The purchase of property located adjacent to the West 32nd Street
Detention Cell also may be necessary to allow for storage capacity expansion.
City of Dubuque, lowa Drainage Basin Master Plan
Bee Branch Drainage Basin 4-10 Fall 2001
BEE BRANCH DRAI'NAGE BASIN
4.2.5.1 Detention
Detention offers a means of controlling major flood events to prevent damage to downstream
propm-ties and infrastructure. Detention basins function by impounding runoff from an upstream
basin and releasing it at a controlled rate to minimize downstream flooding. Within the Bee
Branch Drainage Area, the West 32nd Street Subarea offers the best opportunity for storage.
Table 4.8 summaries the detention sites investigated, while Figure 4-8 depicts the location of the
sites.
Table 4.8
West 32nd Street Drainage Subarea
Detention Sites Investigated
W32-ST-! West 32nd Street The West 32nd Street Detention Cell is an existing detention
Detention Cell cell with a gated outlet control. This site was investigated
further.
W32-ST-9 Grandview Avenue A storage area excavated upstream of the Grandview Avenue
crossing south of West 32nd Street. The site was shown to
produce a small decrease in peak discharge in the reach
immediately downstream of Grandview Avenue. Due to the
limited benefit to a relatively small number of properties
located between Grandview Avenue and the West 32nd Street
Detention Cell, this site was not investigated farther. Greater
~mpacts over a broader area would be realized if these efforts
were focused on expanding storage at the West 32nd Street
Detention Cell.
W32-DET-1 Former Ski Area An earthen embankment constructed within the former ski area
subbasin was investigated. Due to location of rock outcrops,
the dam embankment would be situated in the upper reach of
the subbasin. The contributing drainage area and the storage
volume would be reduced making this site unfavorable. This
site was not investigated further.
W32-DET-2 West 32nd Street An earthen embankment constructed across West 32nd Street
located east of the Carter Blvd and West 32nd Street
intersection. This detention site would control the runoff from
the upper 2/3 of the drainage subarea. This site would require
relocating or eliminating a portion of West 32nd Street and
relocating the Carter Blvd intersection. Several homes located
within the flood pool would be relocated. Due to the extensive
relocations, this site was not investigated further.
City of Dubuque, lowa Drainage Basin Master Plan
Bee Branch Drainage Basin 4-] 1 Fall 2001
BEE BRANCH DRAINAGE BASI*N
Table 4.8
West 32nd Street Drainage Subarea
Detention Sites Investigated
W32-DET-5 West 32nd The West 32nd Street drainage channel along Carter Blvd. is a
Street/Carter natural depressionat area and offers an opportunity to construct
Boulevard an embankment, on the east side of Carter Blvd, to create
detention storage. This would require modifications to the
Carter Blvd. intersection and the construction of a berm parallel
to Carter Blvd. Due to the limited amount of storage, this site
was not investigated further.
W32-ST-12 Carter Boulevard The West 32nd Street drainage channel along Carter Blvd. is a
natural depressional area and offers an opportunity to construct
an embankment, on the west side of Carter Blvd, to create
detention storage. Due to the limited amount of storage, this
site was not investigated further.
W32-DET-3 Arabian Trail Located on the west side of the West 32nd Street drainage
channel along Carter Blvd and near Arabian Trail is a possible
detention storage site. Due to the limited amount of storage,
this site was not investigated further.
W32-DET4 Upper Carter A possible detention site exists where the West 32nd Street
Boulevard drainage channel tums northeasterly along Carter Blvd.
Constructing an earthen embankment and outlet system that
would block the natural ravine in this area would restrict
outflow. Due to the large storage potential and limited
interference with utilities, this site was investigated further.
W32-ST-13 Pedestrian Crossing By increasing the height of the pedestrian crossing berm,
storage can be increased substantially with minor construction.
This site was investigated further.
W32-ST-14 J.F. Kennedy Excavating upstream of J.F. Kennedy would create additional
storage. Due to the potential storage, this site was investigated
further.
W32-ST-15 Northwest Arterial I Modifying the drainage structure by consfficting the existing 4-
! foot opening will increase the peak storage behind the roadway
embankment. The increased flood pool would be restricted to
the park area. This site was investigated further.
Note:
1. See Figure 4-8 for stmctttre identification number.
City of Dubuque, Iowa Drainage Basin Master Plan
Bee Branch Drainage Basin 4-12 Fall 2001
BEE BRANCH DRAI'NAGE BASIN
Table 4.9 presents a summary of the detention improvement alternatives considered for further
investigation. Figure 4-9 shows a layout configuration for the potential detention sites identified.
Each alternative considered either multiple detention cells or one large regional detention
facility. All alternatives assumed the existing outlet works at the West 32nd Street Detention
Cell would be removed and replaced to improve the hydraulics at the outlet. Expanding the
West 32nd Street Detention included excavating, increasing the existing berm elevation, or a
combination of the two. Table 4.10 summarizes the peak 100-year inflow and outflow
discharges resulting from the five (5) improvement alternatives.
Table 4.9
West 32nd Street Subarea
Detention Improvement Alternative Summary
W32-1
W32-2
W32-3
W324
W32-5
Construct multiple upstream detention at J.F. Kennedy, pedestrian bridge, and upper
Carter. Excavate additional storage at West 32nd Detention Cell and remove and
replace outlet structure. Purchase properties located within the 100-year flood pool.
Construct multiple upstream detention at J.F. Kennedy, pedestrian bridge, and upper
Carter. Increase existing berm elevation to provide additional storage at West 32nd
Detention Cell and remove and replace outlet sm~cture. Purchase propeffies located
within the 100-year flood pool.
Construct one large upstream detention at upper Carter. Excavate additional storage at
West 32nd Detention Cell and remove and replace outlet structure. Purchase
properties located within the 100-year flood pool.
Construct one large upstream detention at upper Carter. Increase existing berm
elevation to provide additional storage at West 32nd Detention Cell and remove and
replace outlet structure. Purchase propeRties located within the 100-year flood pool.
Construct one large upstream detention at upper Carter. Increase existing berm
elevation and excavate existing area to provide additional storage at West 32nd
Detention Cell and remove and replace outlet structure. Purchase properties located
within the 100-year flood pool.
The Upper Carter Boulevard (W32-DET-4) location and expansion of the West 32nd Street
Detention Cell (W32-ST-1) are the two primary sources of potential storage capacity within the
West 32nd Street Subarea. A natural ravine area is located along Carter Blvd in the West 32nd
Street Subarea and this natural depressional area offers the opportunity to store the entire
upstream 100-year runoff volume if a controlled gate is installed. Construction of either of these
structures would need to be in accordance with the Iowa Department of Natural Resources, Class
3 dam classification.
City of Dubuque, Iowa Drainage Basin Master Plan
Bee Branch Drainage Basin 4~13 Fall 200J
BEE BRANCH DRAt'NAGE BASt'N
Construction of the three (3) detention cells located upstream of the Northwest Arterial (W32-
ST-15), J. F. Kennedy Road (W32-ST-14) and the pedestrian crossing (W32-ST-13) would
provide similar storage to the construction of the Upper Carter Boulevard detention cell; but at a
greater capital cost. The West 32nd Street Detention Cell has an existing storage capacity of
46.0 acre-feet. Excavation, increasing the earthen berm elevation, or a combination of the two
can obtain additional storage up to 94.0 acre-feet as shown in Table 4.10. Proposed
improvements to the West 32nd Street Detention Cell are shown in Figure 4-10.
Table 4.11 smnmarizes an opinion of probable construction costs for each of the detention
improvement alternatives within the West 32nd Street Subarea. Considering cost and impact on
downstream flows, Alternative W32-5 was determined to be the most efficient and effective
altemative~ This alternative was then used as the basis to develop the downstream alternatives so
a realistic comparison could be made without evaluating a complex matrix of interrelated
options. Impacts from this alternative affecting the Couler Valley area are discussed in
subsequent sections.
Table 4.11
West 32nd Street Subarea
Detention Improvement Alternative and Estimated Construction Cost Summary
W32-1 Construct multiple upstream detention at J.F. Kennedy, pedestrian bridge, $5,250,000
and upper Carter. Excavate additional storage at West 32nd Detention
Cell and remove and replace outlet structure. Purchase properties located
within the 100-year flood pool.
W32-2 Construct multiple upstream detention at J.F. Kennedy, pedes~an bridge, $4,000,000
and upper Carter. Increase existing berm elevation to provide additional
storage at West 32nd Detention Cell and remove and replace outlet
s~yucture. Purchase properties located within the 100-year flood pool.
W32-3 Construct one large upstream detention at upper Carter. Excavate $4,700,000
additional storage at West 32nd Detention Ceil and remove and replace
outlet structure. Purchase properties located within the 100-year flood
pool.
W32-4 Construct one large upstream detention at upper Carter. Increase existing $3,500,000
berm elevation to provide additional storage at West 32nd Detention Cell
and remove and replace outlet structure. Pt~chase properties located
within the 100-year flood pool.
W32-5 ConsWact one large upstream detention at upper Carter. Increase existing $4,700,000
berm elevadon and excavate existing area to provide additional storage at
West 32nd Detention Cell and remove and replace outlet structure.
Purchase properties located within the 100-year flood pool.
Note:
1. Contingencies (25%) were added to account for estimated quantities, unit price adjustments and miscellaneous work
related items. An additional 25% was included for administrative, legal and engineering costs. Rights-of-way,
operation and maintenance and m~ttgat~on costs were not included. Costs based on Iowa Department of Transportation
1999 unit prices.
City of Dubuque, lowa Drainage Basin Master Plan
Bee Branch Drainage Basin 4-15 Fall 2001
BEE BRANCH DRAINAGE BASIN
4.2.S.2 Channel and Drainage Structure Improvements
No opportunity was found to make significant impacts on flood damages through channel or
storm sewer improvements in the West 32nd Street Subarea.
4.2.6 Recommendations for Improvement Alternatives
The program developed for the City of Dubuque consists of the recommended solutions for the
West 32nd Street Drainage Subarea and could be implemented by the City.
It is recommended to implement the items contained in detention improvement alternative W32-
5. This alternative includes construction of one large upstream detention cell at upper Carter,
increasing the existing berm elevation and excavating existing area to provide additional storage
at the West 32nd detention cell, removing and replacing the outlet structure at the West 32nd
Street Detention Cell, and purchasing properties located within the 100-year flood pool of the
West 32nd Street Detention Cell. While this alternative was not the least cost alternative, the
additional incremental impact on flooding is substantial relative to the increased cost.
4.2.7 Project Phasing
The recommended improvements were ranked based on the resulting benefits in comparison to
the costs of improvements. In this manner, the proposed West 32nd Street Subarea
improvements were prioritized, as shown in Table 4.12. It is recommended that detention
improvements at the most upstream areas are built first and then proceed downstream.
City of Dubuque, lowa Drainage Basin Master Plan
Bee Branch Drainage Basin 4-16 Fall 2001
BEE BRANCH DRAINAGE BAS]*N
Table 4.12
West 32nd Street Drainage Subarea
Recommended Improvements Summary
1 Northwest Arterial Modify die drainage structure by constricting the existing 4-foot $3,000
(W32-ST-15) I opaning to increase die peak storage behind die roadway
embankment.
2 Upper Carter BIvd. Construct an earthen embankment and outlet system where die $874,000
(W32-DET4) West 32nd Street drainage channel turns northeasterly along
Carter Blvd. to block die natural ravine area and restrict outflow.
3 West 32nd Street Increase existing berm elevation and excavate existing area to $3,831,000
Detention Cell >rovide additional storage. Remove and replace outlet slructure,
OV32-ST-1) and purchase properties located within the 100-year flood pool.
Total Estimated Capital Cost: $4~700,000
Note:
1. Estimated capital costs include contingencies (25%) to account for estimated quantities, unit price adjustments, and
miscellaneous work related items. An additional 25% was included for administrative, legal, and engineering costs.
Right-of-way, operation and maintenance, and mitigation costs were not included. Costs based on Iowa Department of
Transportation 1999 trait prices.
4.3 KAUFHANN AVENUE DRAINAGE SUBAREA
4.3.1 General Subarea Description
The Kaufmann Avenue Drainage Subarea (Kaufmann Subarea) is located in the west central
portion of the Bee Branch Drainage Area. The drainage subarea measures approximately 1.3
square miles and drains in an easterly direction into the Bee Branch storm sewer mink line
through a 6-foot x 3-foot oval pipe. The drainage area is roughly bounded by Kane Street to the
north, Clarke Drive to the south, Carter Road to the west, and North Main Street to the east.
Elevations in the subarea range from 914 feet in the upper portion to 618 feet at the outlet. The
main drainage path through the subarea follows Kaufmann Avenue, where 'water is conveyed in
the storm sewer and the street. The overall slope along this path is 2 percent.
City of Dubuque, Iowa
Drainage Basin Master Plan
Bee Branch Drainage Basin 4-17 Fall 2001
BEE BRANCH DRAI'NAGE BASI'N
4.3.2 Flood Hydrology
The HEC-HMS model was utilized to compute the peak runoff rates for the 10-year, 50-year,
100-year and 500-year return period storm events. Runoff hydrographs were developed for each
storm event for ultimate development condition, as defined by the sty s comprehensive land use
plan.
Figure 4-11 depicts the subbasin delineation, while Figure 4-12 is a schematic of the HEC-HMS
model. Table 4.13 provides a summary of peak runoff rates for selected storm events at key
locations in the Kaufmann Avenue Drainage Subarea. A summary of the peak runoff rates for
subbasin hydrographs can be found in the Hydrologic and Hydraulic Appendices.
Table 4.13
Kaufmann Avenue Drainage Subarea Peak Runoff Summary
Existing Drainage System Conditions
Kanfmann -~ lain Channel
2 Kaufmann & Heeb 1.30 1,630 2,400 2,8-~----- 3,96-~---
20 Kaufmaun & Hempstead 1.22 1,620 2,370 2,760 3,920
10 Kaufmann & Valeria 1.15 1,600 2,350 2,740 3,880
6 Kaufmann & Kane 1.04 1,530 2,240 2,600 3,680
7 Kaufmunn & Tributary 0.93 1,520 2,210 2,570 3,620
9 Kaufinann & Grandview 0.83 1,480 2,150 2,490 3,500
3 Kaufmann & Grmadview 0.44 820 1,190 1,370 1,930
4 Kaufmann & Tributary (N) 0.34 770 1,120 1,290 1,810
16 Kaufmann & Tributary (S) 0.29 690 990 1,140 1,590
18 Kaufmann & Maryville
Drive 0.22 550 790 910 1,270
12 Kaufmann & Tributary (S) 0.19 500 720 820 1,140
Kaufmann -Tributa No. 1
11 Bunker Hill Golf Course 0.3~-~ 65---~--- 940 1,090 -[ 1,540
14 Bunker Hill Golf Course 0.18 500 740 860 1,210
21 Bunker Hill Road 0.05 180 260 t 290 390
22 St. Ambroise 0.06 160 250 300 430
Notes:
See F~gure 4-t2 for location of HEC-HMS node and identification number.
2. Peak runoff rates bared on ultimate land use conditions and simulation of a 24-hour storm event.
3. Peak discharges re rted are outflows from the s ecified node.
Ci~ofDubuqu~lowa
Bee Branch Drainage Bas~ 4-18 DraYage Bas&MasterPlan
FaH2OOJ
BEE BRANCH DRAZNAGE BASIN
4.3.3 Stream Hydraulics
The main channel is along Kaufmann Avenue, where the storm sewer and the street convey flow.
Flow in tributaries also is conveyed through streets and storm sewer systems. A simplified street
cross-section and Manning's equation were used to determine the hydraulics in the streets on the
main channel and tributaries studied. A rectangular cross-section using the average longitudinal
street slope, curb height, and street width along with a Manning's roughness coefficient of 0.013
was assumed to determine the street or curb full capacity. An average longitudinal street slope
and Manning's equation for full pipe flow determined the capacity of the existing storm sewer
system. The existing hydraulic capacity of the system was equal to the summation of the pipe
and street flow. The total conveyance was then compared to the 2-year and 10-year peak
discharges. The flow in excess of the storm sewer capacity (not including curb full capacity)
was used to size a proposed relief storm sewer system. The additional capacity required for the
proposed relief sewer system was determined by subtracting the existing storm sewer pipe
capacity from the peak discharges for the 2- and 10-year flood events. Manning's equation for
full pipe flow and the existing average longitudinal street slope were used to calculate the pipe
size required for the additional capacity.
A summary of the hydraulic capacity at several locations along the Kaufmann Avenue Drainage
Subarea is presented in Table 4.14. The additional capacity required for a proposed relief sewer
to convey the 2- and 10-year flood events is presented in the two right-hand columns of Table
4.14. Twelve of the storm sewer segments evaluated do not provide the hydraulic capacity
necessary for a 2-year flood event, and all fifteen storm sewer segments analyzed fail to provide
the hydraulic capacity needed for a 10-year flood.
4.3.4 Problem Areas
The hydrologic and hydraulic analyses provided the information needed for identification of
areas not in compliance with the City's drainage standards/criteria. The frequency and hazards
associated with particular flood events must be taken into account; therefore, the flood protection
required may vary from street to street. Consequently, the sizing of storm sewers must be
performed on a case-by-case basis, while considering the impact of each portion on the entire
system.
City of Dubuque, lowa
Bee Branch Drainage Basin 4-19 Drainage Basin Master Plan
Fall 2001
BEE BRANCH DRAINAGE BASIN
4.3.5 Development of Alternative Solutions
Because the Kaufmann Avenue Drainage Subarea is located in the upland areas of the Bee
Branch basin, construction of detention cells could potentially have an effect on flooding in the
Couler Valley area. Detention storage in the upper portion of the subarea would provide relief
where development has exceeded the capacity of the storm water conveyance system located
downstream. Expansion of the capacity of storm sewer inlets and pipes may also significantly
reduce flooding streets and adjacent properties within the Kaufmann Avenue Drainage Subarea.
4.3.5.1 Detention
While detention storage in the Kaufmann Avenue Drainage Subarea may have a significant
impact on flooding problems in the Couler Valley area, few potential sites for construction of a
detention cell exist. Only one site in the Kaufmann Avenue Drainage Subarea was identified as a
possible location for a detention cell. The site is located on the roadway connecting Grandview
Avenue and Kaufmann Avenue (Grandview/Kaufmann connector), as shown in Figure 4-13. To
take advantage of the storage volume available at this location, an earthen embankment would be
constructed across the roadway, thereby eliminating the Grandview/Kaufmann connector.
During extreme storm events, the Grandview Avenue intersection would be closed to traffic and
a detour would be posted on the approaching segment of each roadway.
The proposed embankment would pond water on Grandview to the northwest and south up to an
elevation of approximately 720 feet. This is approximately the elevation at which water would
begin to spill over the crest of the hill on Grandview Avenue. A maximum volume of 43.5 acre-
fi would be stored at this elevation.
The impact of the construction of this detention cell was evaluated by modifying the HEC-I-IMS
hydrologic model. The stage-storage relationship for the detention cell was estimated using
topographic information from the DAGIS. Stage-discharge data was created assuming a 48-inch
reinforced concrete pipe outlet with inlet control using FHWA nomographs and orifice discharge
equations.
The 100-year peak inflow to the proposed Grandview/Kaufmann Detention Cell was estimated at
1,120 cfs. The storage provided by the proposed detention cell attenuated the peak discharge by
855 cfs (76%), to 265 cfs, immediately downstream of the detention cell and reduced the peak
discharge by 30% (from 2,800 cfs to 1,950 cfs) at the outlet of the Kaufmann Avenue Subarea.
However, flooding may still occur downstream because of the coincidence in peak discharges
fi'om adjacent subareas.
City of Dubuque, lowa
Bee Branch Drainage Basin 4-21 Drainage Basin Master Plan
Fall 2001
BEE BRANCH DRAINAGE BASIN
Construction of this detention cell would result in maximum ponding depths on Grandview
Avenue up to 20 feet, so safety issues must be addressed. During storm events, the impacted
section of Grandview Avenue would be closed to traffic. A system of advanced warning signs
and barricades alerting people to the danger as well as prohibiting access to the area would be
installed. The estimated cost for the Grandview/Kaufmann Detention Cell is approximately
$530,000. A detailed breakdown of this cost estimate is provided in the Opinion of Probable
Construction Costs Appendix.
4.3.5.2 Channel and Drainage Structure Improvements
The hydraulic capacities (pipe sizes) required for conveyance of the 2-year and 10-year flood
events are reported in Table 4.14.
4.3.6 Recommendations for Improvement Alternatives
The program developed for the City of Dubuque consists of recommended solutions for the
Kaufmann Avenue Drainage Subarea and could be implemented by the City. It is recommended
to implement the proposed Grandview/Kaufmann Detention Cell. This proposal includes
construction of a 20- to 25-foot earthen berm, installation of a 48-inch RCP outlet structure, and
providing adequate advanced warning signs and proper street lighting.
4.3.7 Project Phasing
The only recommendation for the Kanfmann Avenue Drainage Subarea is the proposed
Grandview/Kaufmann Detention Cell; therefore, no project phasing is required for the Kaufmann
Avenue Drainage Subarea at this time. The recommended improvement is summarized in Table
4.15.
Table 4.15
~enue Drainage Subarea
Recommended Improvements Summary
Note:
1 GrandviewFKaufmarm
Detention Cell
Construct 20- to 25-foot earthen berm, install 48- $530,000
inch RCP outlet structure, and provide adequate
and lighting.
$530,000
Total Estimated Capital Cost:
Estimated capital costs include contingencies (25%) to accotmt for estimated quantifies, unit price adjustments, and miscellaneous
work r~lated items. An .a~di~ona125% was included for adralnislrative, legal, and eng/neering costs. Right-of-way, operation
and rmuntenance, and ma~gatmn costs were not included. Costs based on Iowa Department of Tr.~=~.~.~spor t atioa 1999 unit prices
City of Dubuque, Iowa
Bee Branch Drainage Basin 4-22 Drainage Basin Master Plan
Fall 2001
BEE BRANCH DRAINAGE BASIN
4.4 LOCUST STREET DRAINAGE SUBAREA
4.4.1 General Subarea Description
The Locust Street Drainage Subarea (Locust Subarea) is located in the upper reaches of the Bee
Branch Drainage Subarea. The drainage subarea measures approximately 0.9 square miles and
drains into the Bee Branch storm sewer trunk line through a 10.5-foot x 15-foot RCB. The
drainage area is roughly bounded by Clarke Drive to the north, University Avenue to the south,
Avoca Street to the west, and Central Street to the east.
Elevations in the subarea range from 900 feet in the upper portion to 620 feet at the outlet. The
main drainage path through the subarea follows Locust Street, where water is conveyed in the
storm sewer and the street. The overall slope along this path is 2 percent.
4.4.2 Flood Hydrology
The HEC-HMS model was utilized to compute the peak runoff rates for the 10-year, 50-year,
100-year and 500-year return period storm events. Runoff hydrographs were developed for each
storm event for ultimate development conditions, as defined by the City's comprehensive land
use plan.
Figure 4-14 depicts the subbasin delineation, while Figure 4-15 is a schematic of the HEC-HMS
model. Table 4.16 provides a summary of peak runoff rates for selected storm events at key
locations in the Locust Subarea. A summary of the peak runoff rates for all sub-basin
hydrographs can be found in the Hydrologic and Hydraulic Appendices.
Table 4.16
Locust S~ee.t ~ba~rea Peak Runoff Summary I
~rasting Drainage System Conditions ---~ ~
8 Locust and Pierce 0.70
1,130 1,340 1,960
City. of Dubuque, lowa
Bee Branch Drainage Basin 4-23 Drainage Basin Master Plan
Fall 2001
BEE BRANCH DRAINAGE BASIN
Table 4.16
Locust Street Drainage Subarea Peak Runoff Summary
Existing Drainage System Conditions
6 Locust and Kirkwood 0.64 690 1,060 1,260 1,840
5 Locust and Rosedale 0.54 650 990 1,180 1,720
7 Rosedale and Glen Oak 0.44 520 800 960 1,400
10 Rosedale and Adair 0.29 360 560 660 970
12 Alta Place 0.05 70 100 120 180
Locust- Trlbutar No. 1 --
~dCox ~ 0.04 ~ 60 ~ 170
Locust- Tributar No. 2
Locust- Tributar No. 3
~andGrandview I 0.05 [ 70 ] 100 ~ 180
Notes:
1. See Figure 4-15 for location of HEC-HMS node and identification number.
2. Peak runoff rates based on ultimate land use conditions and simulation of a 24-hour storm event.
3. Peak discharges reported are outflows from the specified node.
4.4.3 Stream Hydraulics
The main channel is along Locust Street, where the storm sewer and the street convey flow.
Flow in tributaries also is conveyed through streets and storm sewer systems. A simplified street
cross-section and Manning's equation were used to determine the hydraulics in the streets on the
main channel and tributaries studied. A rectangular cross-section using the average longitudinal
street slope, curb height, and street width along with a Manning s roughness coefficient of 0.013
was assumed to determine the street or curb full capacity. An average longitudinal street slope
and Manning's equation for ~ull pipe flow determined the capacity of the existing storm sewer
system. The existing hydraulic capacity of the system was equal to the summation of the pipe
and street flow. The total conveyance was then compared to the 2-year and 10-year peak
discharges. The flow in excess of the storm sewer capacity (not including curb full capacity)
was used to size a proposed relief storm sewer system. The additional capacity required for the
proposed relief sewer system was determined by subtracting the existing storm sewer pipe
capacity from the peak discharges for the 2- and 10-year flood events. Manning's equation for
Ci~ofDubuque, Iowa
Bee Branch Drainage Bas~ 4-24 DraYage Basin MasterPlan
Fall2001
BEE BRANCH DRAI'NAGE BASI'N
full pipe flow and the existing average longitudinal street slope were used to calculate the pipe
size required for the additional capacity.
A summary of the hydraulic capacity at several locations along the Locust Subarea is presented
in Table 4.17. The additional capacity required for a proposed relief sewer to convey the 2- and
10-year flood events is presented in the two right-hand columns of Table 4.17. Seven of the
storm sewer segments evaluated do not provide the hydraulic capacity necessary for a 2-year
flood event, and all thirteen storm sewer segments analyzed, except for the Vernon Street
segment, fail to provide the hydraulic capacity needed for a 10-year flood.
4,4.4 Problem Areas
The hydrologic and hydraulic analyses provided the information needed for the identification of
areas not in compliance with the City's drainage standards/criteria. The frequency and hazards
associated with particular flood events must be taken into account; therefore, the flood protection
required may vary from street to street. Consequently, the sizing of storm sewers must be
performed on a case-by-case basis, while considering the impact of each portion on the entire
system.
An evaluation of the existing storm sewer system along Rosedale Avenue from Grandview
Avenue to Locust Street was performed for the 2-year and 10-year flood events. This segment of
storm sewer corresponds to HEC-ItMS nodes 6, 5, 7, 10, and 12 in Table 4.16 and 4J7. The
hydraulic capacities presented in Table 4.17 are for a relief sewer to supplement the existing
system. The pipe capacity required for a complete replacement of the existing sewer system also
was performed. The results of this analysis are presented in Table 4.18 for the 2-year and 10-
year flood events.
City of Dubuque, Iowa
Drainage Basin Master Plan
Bee Branch Drainage Basin 4-25 Fall 2001
BEE BRANCH DRAINAGE BASIN
Table 4.18
Locust Street Drainage Subarea
Hydraulic Capacity for Storm Sewer Replacement
Locust Stree i-Main Channel ~
Locust& 60 310 ~ 66~ 84
6 Kirkwood ~ __-- ~
~ Locust & 36 - 72 300 650 60 78
5
Rosedale
Rosedale & 36 - 42 240 520 54 66
7 Glen Oak
Rosedale & 15 160 360 42 60
I0 Adair
12 Alta Place 24 - 36 30 70 24 30
Notes:
1. See Figure 4-15 for location of HEC-HMS node and identification number.
2. Total capacity required for replacement of existing storm sewer. ~
4.4,5 Development of Alternative Solutions
Although alternatives were developed to address the special problem area along Rosedale
Avenue, general alternatives focused on the entire subarea were not established. No available
sites for regional detention exist because of the topography and land use of the Locust Subarea.
It should also be noted that the expansion of the capacity of storm sewer inlets and pipes might
significantly reduce street and property flooding within the Locust Subarea.
4.4.5.1 Detention
Regional detention is not viable within the Locust Subarea, as the subarea is fully developed.
4.4,5.2 Channel and Drainage Structure Improvements
The hydraulic capacity (pipe sizes) required for conveyance of the 2- and 10-year flood events
are reported in Tables 4.17 and 4.18.
City of Dubuque, Iowa
Bee Branch Drainage Basin
4-27
Drainage Basin Master Plan
Fall 2001
BEE BRANCH DRAINAGE BASIN
4.4.6 Recommendations for Improvement Alternatives
The sizing of individual storm sewers should be performed on a case-by-case basis. The
potential for flood damage posed by the various storm events should be weighed against the cost
of improvement.
4.4.7 Project Phasing
No project phasing is required for the Locust Subarea at this time.
4.5 CENTRAL BUSINESS DISTRICT - NORTH SUBAREAS
4.5.1 General Subarea Description
The Central Business District - North Drainage Subareas (Central Business District - North) are
located in the center of the Bee Branch Drainage Subarea and includes Washington Street,
Windsor, Hamilton, Dock and Upper Kerper Drainage Subareas. The drainage subarea
measures approximately 1.9 square miles and is roughly bounded by West 32nd Street to the
north, 17th Street to the south, Central Street to the west, and Peosta Channel to the east.
Elevations in the subarea range from 644 feet in the upper portion to 594 feet at the 16th Street
Detention Cell. The main drainage path through the subarea follows Washington Street, where
water is conveyed in the storm sewer and the street. The overall slope along this path is 0.5
percent.
The main Bee Branch storm sewer trunk line is the main channel in the Bee Branch Drainage
Area. The storm sewer begins approximately 625-feet west of the intersection of West 32nd
Street and Saunders Street then travels in a southeasterly direction to Washington Street and 28th
Streets, as shown in Figures 4-18A and 4-18B. The trunk line then follows Washington Street to
24th Street where the alignment changes to Elm Street. Near 21st Street the alignment leaves the
street and transverses under commercial and industrial properties to its outflow into the 16th
Street Detention Cell. The storm sewer begins as a 10-foot by 9-foot concrete arch and
terminates as a 20-foot x 12-foot stone box. The City has inspected and cleaned the storm sewer
within the last couple of years and has rated the condition of the storm sewer as "good". The
total length of the truck line is approximately 10,400-feet and the pipe falls approximately 40
feet over its length for an average slope of 0.4%.
Numerous collector storm sewers enter into the Bee Branch trunk line system. The West 32nd,
Kaufmann, and Locust Subareas all intersect the Bee Branch trunk line storm sewer system with
a variety of collector pipe sizes. The largest collector pipe is a 10.5-foot x 15-foot reinforced
Drainage Basin Master Plan
City of Dubuque, Iowa Fall 2001
Bee Branch Drainage Basin 4-28
BEE BRANCH DRAI'NAGE BASIN
concrete box draining the Locust Subarea entering the Bee Branch trunk line at 15th and
Sycamore Streets. A 10-foot x 9-foot concrete arch pipe discharges into the Bee Branch trunk
line from the West 32nd Subarea, and a 6-foot x 3-foot oval pipe drains the Kanfmann Subarea
into the Bee Branch trunk line. Several 12-inch pipes also join the trunk line in the upper portion
of the storm sewer trunk line.
The 16th Street Detention Cell is located at the outlet of the Bee Branch trunk line storm sewer.
It is an interior drainage ponding area adjacent to and protecting the Couler Valley area from
Mississippi River floodwaters. The 16th Street Detention Cell pump station is an outdoor
installation consisting of two pumps rated at 90,000-gpm at an 18.7-foot total dynamic head
(TDH) and one pump rated at 20,000-gpm at a 25.4-foot TDH. Twin 12-foot by 12-foot box
culverts serve as a gravity outlet into the Peosta Channel. During periods of high river stages,
the culverts are closed on the riverside with sluice gates mounted on the discharge headwall of
the outlets. When the gates are closed, the culverts serve as a sump and intake bay for the
pumps.
4.5.2 Flood Hydrology
The I-EEC-HMS model was utilized to compute the peak runoff rates for the 10-year, 50-year,
100-year and 500-year return period storm events. Runoff hydrographs were developed for each
storm event for ultimate development conditions, as defined by the City's comprehensive land
use plan. Washington Street is the primary street where the Bee Branch storm sewer trunk line is
located. The ItEC-I-IMS model was used to route hydrographs to the Bee Branch storm sewer
trunk line. Where subareas feed into the Bee Branch storm sewer trunk line, the hydrographs
were exported from I-EEC-HMS to XP-SWMM. The XP-SWMM model was then used to route
and combine hydrographs along the Bee Branch storm sewer trunk line itself.
Figure 4-16 depicts the subbasin delineation, while Figure 4-17 is a schematic of the HEC-HMS
model. Tables 4.19 and 4.20 provide a summary of peak runoff rates for selected storm events at
key locations in the Central Business District - North. A sttmmary of the peak runoff rates for
the subbasin hydrographs can be found in the Hydrologic and Hydraulic Appendices.
Drainage Basin Master Pla,
City of Dubuque, lowa Fall 2001
Bee Branch Drainage Basin 4-29
BEE BRANCH DRAI'NAGE BASI'N
Table 4.19
Central Business District - North Drainage Subareas
Peak Runoff Summary for Existing Drainage System Conditions
Windsor Avenue- Main Channel
24th Streeta_nO 0.39
BB_17 Washington ~~~
53 ~ Windsor and Burden 0.27 1,020
I-Iamilton Street-Main Channel
hannei 15° 230 I 2a0 420
_Dock Street - Main Channel
Dock Ieeosta Charmel I0'16 I180128013201470
Upper Kerl~er
16th Street Detention 0.24 150 240 290 440
Upper Kerper Cell
15th Street and 0.05 50 70 80 120
BB_27B Sycamore
Notes:
1. Peak ranoff rates based on ultimate land use conditions and s~mulat~°n °f a 2ZPh°ur st°rm event
2. See Figure 4_ 17 for location of HEC-HMS node and identificali°n number'
3. Peak discharges repo~ted are outflows from the specified n°de'
4. See Table 4.20 for peak ranoff rates along Bee Branch mink line'
5. Peak ddschaxges fr°m subareas and subbasins calculated in HEC'HMS; peak discharges al°ng Bee Branch st°tm sewer
mink line calculmed in XP-SWMM. ~
4.5.3 Stream Hydraulics
The complexity and importance of the Bee Branch storm sewer trunk line suggested a separate,
detailed analysis should be performed. The Bee Branch storm sewer trunk line was analyzed
using an XP-SWMM model, and a simplified street cross-section and Manning' s equation were
used to analyze the hydraulics of other storm sewers and streets not directly impacted by the
main Bee Branch trunk line.
Drainage Basin Master Plu,~
City of Dubuque, Iowa 4-30 Fall 2001
Bee Branch Drainage Basin
BEE BRANCH DRAINAGE BASIN
4.5.3.1 XP-SWMM Analysis
XP-SWMM is a proprietary program developed by XP Software and is an enhanced version of
the Environmental Protection Agency (EPA) Storm Water Management Model (SWMM). XP-
SWMM models unsteady closed conduit and open channel flow using a series of links and
nodes. Links represent pipe segments and channel reaches, while nodes represent manholes,
junctions, and storage cells. Nodes connect links to create linear, branched, or looped systems
making it possible to model complex networks of pipes and channels.
An XP-SWMM model was developed to assess flooding problems along the Bee Branch trunk
line located in the Couler Valley area of the City of Dubuque. The Bee Branch trunk line model
contains several broad assumptions and is intended to be a useful tool in evaluating altemative
flooding impacts.
4.S.3.1.1 Model Assumptions
Main Storm Sewer Trunk line
The model geometry of the Bee Branch trunk line was based on profile drawings provided by the
City. Information available on this profile included slope, shape, size and material of the
segments making up the mink line. Twenty-eight (28) nodes were created in the XP-SWMM
model where a change in slope, shape, size or material occurred. Several additional nodes were
inserted where minor tributary sewer lines connected to the main line and it was not reasonable
to shift the junction to the next upstream node. The twenty-eight (28) nodes along the main
trunk line of the storm sewer are shown in Figures 4-18A and 4-18B.
Friction losses in XP-SWMM are calculated based on Manning's roughness coefficients. In
general, minor losses were not considered on the main truck line storm sewer. Losses at
manholes were neglected because manholes do not involve expansion and contraction of flow.
Manholes are not a barrel section, but are a tap in the top of the conduit and are small relative to
the conduit cross-section. Junction losses were also neglected due to the small amount of flow
coming from the tributaries relative to the flow in the main trunk line. In cases where major
bend losses were apparent, an equivalent Manning's roughness coefficient in the link where the
bend occurs was calculated to include these effects. Where pipe size changed by more than 20%,
entrance or exit losses were included to account for contraction or expansion of flow. Expansion
and contraction coefficients of 0.7 and 0.3 were used respectively. Entrance and exit loss
coefficients of 0.5 and 1, respectively, were used for flows entering and exiting detention cells.
Inlets along the main trunk line were assumed to have negligible capacity based on field
observations and were, therefore, not modeled. Each node along the main line was "sealed" to
prevent overflow along the main trunk line and force any excess flow into the streets via the
Drainage Basin Master Plan
City of Dubuque, lowa Fall 200J
Bee Branch Drainage Basin 4-32
BEE BRANCH DRAI'NAGE BASI'N
tributary pipes. Generally, very few inlets exist along the main trunk line and the majority of the
inlets are located along the tributaries. See Connection Between Storm Sewer and Street for
further discussion.
Tributary Storm Sewer Lines_
Tributaries to the main trunk line were identified using the DAGIS. Tributary pipes were
assumed to have a slope of 0.5% based on the slope from two representative storm sewers. A
50-foot section of each pipe was included in the model to partition inflow hydrographs between
the main trunk line and the street and to allow flow to reenter the trunk line when capacity is
available. See Connection Between Storm Sewer and Street for further discussion.
Streets_
The street geometry was approximated with a simplified rectangular cross-section consisting of a
33-foot wide street (based on aerial photos) with a 1-foot high curb (based on field observation)
and a 16.5-feet overbank on either side of the street (based on aerial photos), or a total flow
width of 66-feet. When effective flow was anticipated across more than one street, differences in
elevation between streets inverts were taken from the DAGIS and used to create a representative
cross-section. The effective flow area was limited to a single street cross-section in the upper
portion of the trunk line, then changed to a double street cross-section near Jackson Street and
finally to a triple street cross-section near 15th Street to the 16th Street Detention Cell.
In general, invert elevations for the street sections were based on the ground profile elevations
described on the storm sewer profile sheets provided by the City. Reach lengths were based on
the steepest path through the Couler Valley area determined from the DAGIS. Where the
steepest path differed significantly from the path of the trunk line, elevations were established by
the DAGIS. Typically, the steepest path follows the main trunk line of the storm sewer, but near
20th and Elm, where the storm sewer tums to the southeast, the steepest path continues to follow
Elm and then 15th Street to the 16th Street Detention Cell. Links representing the streets were
connected to links representing the tributary sewer pipes allowing for exchange of flow between
the street and the sewer.
Connection Between Storm Sewer and Street
The connections between the storm sewer and the street are modeled in the nodes common to the
tributary storm sewer pipe and street. Inlet capacity was neglected and the connection merely
consists of two street links perched above the sewer link at the same node. Inflow hydrographs
were input at these nodes. When the capacity of either the main or tributary storm sewer limits
inflow, water is forced into the street and when capacity is not limited in the pipe, water from the
street can enter or reenter the storm sewer. Inlets directly connected to the main storm sewer line
Drainage Basin Master Plan
City of Dubuque, Iowa Fall 200J
Bee Branch Drainage Basin 4-33
BEE BRANCH DRA[NAGE BASIN
were assumed to have a negligible effect based on field observations and were not modeled;
therefore, connections only exist at the upstream end of each tributary pipe.
16th Street Detention Cell
The 16th Street Detention Cell's stage-storage relationship is based on information obtained
from the U.S. Army Corps of Engineers (USACE), Rock Island District Design Memorandum,
dated 1966. Water surface elevations in the cell are dependent on Mississippi River stage and
operation of the outlet works.
The 16th Street Detention Cell outlet works were designed to discharge interior drainage by
gravity at low Mississippi River stages and pump at high Mississippi River stages. The modeled
outlet works geometry, twin 12-foot x 12-foot RCBs, is based on information contained in the
USACE Design Memorandum. During high river stages, the outlet is sealed with sluice gates
and flows are diverted over the leyee by three (3) pumps: two 90,000-gpm pumps, rated at 18.7-
feet total dynamic head (TDI-i), and one 20,000-gpm pump, rated at 25.4 TDH. The geometry
and pump curves for the 90,000-gpm pumps are based on information in the USACE Design
Memorandum. Less information was available on the 20,000-gpm pump, and its pump curve
was assumed to have the same characteristics as the other pumps. All three pumps operate
simultaneously with a minimum water surface elevation of 591.5 feet (below 591.5 feet,
cavitation occurs).
Diversions
Three (3) subareas are diverted directly into the 16th Street Detention Cell during high
Mississippi River stages. Depending on the tailwater condition created by the Mississippi River,
different hydrographs were applied to XP-SWMM Node 28. The following subareas and
diversion elevations are as follows:
· 8th Street Subarea- 598.5 feet
· Dock Street Subarea- 600.5 feet
· Hamilton Street Subarea - 603.5 feet
4.5.3.1.2 16th Street Operating Scenarios
Three (3) operating scenarios: normal, current and minimum, were modeled based on the
following constraints:
1. Normal Operatin~ Conditions. Mississippi River water surface elevation is 594.3
feet or the elevation in which 50% of the time the Mississippi River is equal to or
exceeded. Hamilton Street, Dock Street and 8th Street Subareas are not diverted to
City of Dubuque, Iowa Drainage Basin Master Plan
Bee Branch Drainage Basin 4-34 Fall 2001
BEE BRANCH DRAINAGE BASt'N
the 16th Street Detention Cell at elevation 594.3; therefore, they are not included in
this operating scenario.
Current Gate Closure Operatin~ Conditions. The City's current operating procedure
is to close the sluice gates when the Ivlississippi River's water surface elevation is at
598.5 feet. Only 8th Street Subarea is diverted at elevation 598.5; therefore, it was
included in this operating scenario.
Minimum Water Surface Elevation Operating Conditions. The minimum allowable
water surface elevation in the 16th Street Detention Cell is at elevation 591.5 feet.
This scenario assumes the Mississippi River water surface elevation is at or above
the gate closure elevation and the 16th Street Detention Cell was pumped down to
elevation 591.5 feet in anticipation of large storm water discharges. Also, 8th Street
Subarea flows are diverted to the 16th Street Detention Cell under this scenario
because the Mississippi River water surface elevation is assumed to be at or above
the gate closure elevation.
4.5.3.1.3 Street Flooding Depths
The XP-SWMM model, assuming normal operating conditions, provides a depth of flooding or
ponding at various nodes along the Bee Branch storm sewer trunk line. Figure 4-5 depicts the
limits and depth of ponding along the Bee Branch main trunk line. The greatest depth of
ponding is between 24th Street and the 16th Street Detention Cell. Table 4.21 summaries the
depth of flooding for the 10-, 50- and 100- year events. In addition, from Table 4.21 it is noted
that the Bee Branch storm sewer trunk line system has a capacity of less than the 10-year storm
event.
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Bee Branch Drainage Basin 4-35 Fall 2001
BEE BRANCH DRAI'NAGE BASi'N
Table 4.21
Central Business District - North Drainage Subareas
Existing Hydraulic Capacity Summary
Washington Street Dralnao, e Subarea
28 16th Street Detention Cell2 8.02 10.6 12.9
27 15th Street and Railroad3'~ 0 0 0.7
24 19th and Elm3 1.5 4.0 4.7
19 22nd Street and Elm 3.4 4.8 5.5
17 ~4th Street and Elm 2.7 4.2 5.0
14 g6th Street and Jackson3 0.5 1.8 2.2
12 27th Street and Jackson3 0.2 1.8 2.2
8 30th Street and Jackson3 0 1.7 2.2
West 32nd Street and Saunders 0 1.7 2.1
2 Street
1 West 32nd Street Detention Cell2 11.0 13.5 13.8
Notes:
1. Depth of ponding based on rectangular stxeet section, average longitudinal slzeet slope and peak discharge.
2. Depth of ponding represents peak stage in detention cell.
3. Street node location differs from storm sewer node location.
4. Depth of ponding represents depth of overtopping at railroad. Railroad profile is elevated relative to surrounding
topography-
4.5.3.2 Manning's Analysis
The main channel is along Washington Street, where the storm sewer and the street convey flow.
Flow in tributaries also is conveyed through streets and storm sewer systems. A simplified street
cross-section and Manning's equation were used to determine the hydraulics in the streets on the
main channel and tributaries studied. A rectangular cross-section using the average longitudinal
street slope, curb height, and street width along with a Manning's roughness coefficient of 0.013
was assumed to determine the street or curb full capacity. An average longitudinal street slope
and Manning's equation for full pipe flow determined the capacity of the existing storm sewer
system. The existing hydraulic capacity of the system was equal to the summation of the pipe
and street flow. The total conveyance was then compared to the 2-year and 10-year peak
discharges. The flow in excess of the storm sewer capacity (not including curb full capacity)
was used to size a proposed relief storm sewer system. The additional capacity required for the
Drainage Basin Master Plan
City of Dubuque, Iowa
Bee Branch Drainage Basin 4-36 Fall 2001
BEE BRANCH DRAi'NAGE BASIN
proposed relief sewer system was determined by subtracting the existing storm sewer pipe
capacity from the peak discharges for the 2- and 10-year flood events. Manuing's equation for
full pipe flow and the existing average longitudinal street slope were used to calculate the pipe
size required for the additional capacity.
A summary of the hydraulic capacity at several locations along Windsor, Hamilton, and Dock
Subareas is presented in Table 4.22. The additional capacity required for a proposed relief sewer
to convey the 2- and 10-year flood events is presented in the two right-hand columns of Table
4.22. Some of the storm sewer segments evaluated do not provide the hydraulic capacity
necessary for a 2- or 10-year flood event.
4.5.4 Problem Areas
The flood hydrologic and hydraulic analyses provide the information needed for identification of
areas not in compliance with the City's drainage standards/criteria. The frequency and hazards
associated with particular flood events must be taken into account; therefore, the flood protection
required may vary from street to street. Consequently, the sizing of storm sewers must be
performed on a case-by-case basis, while considering the impact of each portion on the entire
system.
The City requested analysis of a particular problem area in the Windsor Subarea. An evaluation
of the existing storm sewer system along Windsor Avenue from Burden Street to Sutter Street
was performed for the 2-year and 10-year flood events. The hydraulic capacities presented in
Table 4.22 are for a relief sewer to supplement the existing system. The pipe capacity required
for a complete replacement of the existing sewer system also was performed. The results of this
analysis are presented in Table 4.23 for the 2-year and 10-year flood events. The existing sewer
system consists of a 36-, 24-, 48-, and 54-inch system starting at the intersection of Burden and
Windsor. According to the analysis summarized in Table 4.23, a 48-inch pipe would be required
to convey the 2-year event or a 66-inch pipe to convey the 10-year event.
City of Dubuque, lowa Drainage Basin Master Plan
Bee Branch Drainage Basin 4-37 Fall 2001
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)ii
BEE BRANCH DRAI'NAGE BASTN
Table 4.23
Central Business District - North Drainage Subareas
Hydraulic Capacity for Storm Sewer Replacement
Windsor Avenue - Main Channel
BB_17 24th and Elm 54 240 490 54 66
Windsor and
53 12 - 24 210 430 48 66
Burden
Notes:
1. See Figure 4-17 for location of HEC-HMS node and identilication number.
2. Total capacity required for replacement of existing storm sewer.
The combination of an inadequate conveyance system and poor drainage from the flat
topography produces the undesirable flooding conditions shown in Figure 4-5 for the 100-year
flood event. The alternative improvements to the Bee Branch storm sewer trunk line will be
discussed in Section 4.7 in more detail.
4.5.5 Development of Alternative Solutions
Although alternatives were developed to address the special problem area along Windsor
Avenue, general alternatives focused on the entire subarea were not established. No available
sites for regional detention exist because of the topography and land use of the Central Business
District - North. Increasing the capacity of storm sewer inlets and pipes will significantly reduce
street and property flooding within the Central Business District - North. Further development
of alternatives in the Washington Street Subarea is discussed in Section 4.7.
4.5.5.1 Detention
While the 16th Street Detention Cell has a significant impact on the Bee Branch Drainage Basin,
few detention sites exist within the Central Business District - North. Table 4.24 summarizes
the existing 16th Street Detention Cell storage capacity. Topographic constraints prohibit
enlarging the capacity of the 16th' Street Detention Cell.
City of Dubuque, Iowa Drainage Basin Master Plan
Bee Branch Drainage Basin 4-39 Fall 2001
BEE BRANCH DRAINAGE BASIN
Table 4.24
Central Business District - North Drainage Subareas
Detention Storage Summary
16th Street
6.4 63 595
Detention Cell
Additional storage not
viable due to topographic
constraints.
4.5.5.2 Channel and Drainage Structure Improvements
The hydraulic capacities (pipe sizes) required for conveyance of the 2- and 10-year flood events
are reported in Tables 4.22 and 4.23. Other conveyance improvements for the Bee Branch
Drainage Basin are discussed in Section 4.7.
4.5.6 Recommendations for Improvement Alternatives
No recommendations are presented for the Central Business District - North; however, specific
recommendations are discussed in Section 4.7 for the Bee Branch Drainage Basin.
4.5.7 Project Phasing
No project phasing is required for the Central Business District - North.
4.6 CENTRAL BUSINESS DISTRICT SUBAREAS
4.6.1 General Subarea Description
The Central Business District Drainage Subareas (Central Business District) are located in the
lower reaches of the Bee Branch Drainage Subarea and includes 8th Street, llth Street, 14th
Street and Lower Kerper Drainage Subareas. The drainage area measures approximately 0.9
square miles and is roughly bounded by 15th Street to the north, 5th Street to the south, Alpine
Street to the west, and the Peosta Channel to the east.
Elevations in the subarea range from 902 feet in the upper portion to 594 feet at the 16th Street
Detention Cell. The main channel through the subareas follows 8th, llth, and 14th Streets,
where water is conveyed in the storm sewer and street. The overall slope along the main channel
is 4 percent.
City of Dubuque, Iowa Drainage Basin Master Plan
Bee Branch Drainage Basin 440 Fall 2001
BEE BRANCH DRAINAGE BASIN
4.6.2 Flood Hydrology
The HEC-HMS model was utilized to compute the peak runoff rates for the 10-year, 50-year,
100-year and 500-year return period storm events. Runoff hydrographs were developed for each
storm event for ultimate development conditions, as defined by the City's comprehensive land
use plan.
Figure 4-19 depicts the subbasin delineation, while Figure 4-20 is a schematic of the HEC-HMS
model. Table 4.25 provides a summary of peak runoff rates for selected storm events at key
locations in the Central Business District. A summary of the peak runoff rates for alt subbasin
hydrographs can be found in the Hydrologic and Hydraulic Appendices.
Table 4.25
Central Business District Drainage Subareas Peak Runoff Summary
Existing Drainage System Conditions
Lower Kerp_~
16th St. Detention Cell and
96 j Kerper Blvd. I 0'42I 450 [ 650 i '60 [1'060
8th Street - Main Channel
8th and Washington
8th and White
103
116
0.41 320 480 570 830
0.34 310 480 570 830
llthStreet -Main Channel
14thStreet-MainChannel
98 ~14thandU.S. Hwy61 [ 0.12 [ 130 I 200 ~ 240 [ 340
15th Street - Main Channel
BB-27A 1 15th and Sycamore ~ 0.04[ 60 I 80[
Notes:
1. See Figure 4-20 for location of HEC-HMS node and identification number.
2. Peak runoff rates based on ultimate land use conditions and simulation of a 24-hour storm event.
3. Peak discharges reported are outflows from the specified node.
100
130
City of Dubuque, Iowa Drainage Basin Master Plan
Bee Branch Drainage Basin 4-41 Fall 2001
BEE BRANCH DRAINAGE BASIN
4.6.3 Stream Hydraulics
The main channel is along 8th, llth, and 14th Streets, where the storm sewer and the street
convey flow. Flow in tributaries is also conveyed through streets and storm sewer systems. A
simplified street cross-section and Manning's equation were used to determine the hydraulics in
the streets on the main channel and tributaries studied. A rectangular cross-section using the
average longitudinal street slope, curb height, and street width along with a Manning's roughness
coefficient of 0.013 was assumed to determine the street or curb full capacity. An average
longitudinal street slope and Manning's equation for full pipe flow determined the capacity of
the existing storm sewer system. The existing hydraulic capacity of the system was equal to the
summation of the pipe and street flow. The total conveyance was then compared to the 2-year
and 10-year peak discharges. The flow in excess of the storm sewer capacity (not including curb
full capacity) was used to size a proposed relief storm sewer system. The additional capacity
required for the proposed relief sewer system was determined by subtracting the existing storm
sewer pipe capacity from the peak discharges for the 2- and 10-year flood events. Manning's
equation for full pipe flow and the existing average longitudinal street slope were used to
calculate the pipe size required for the additional capacity. A summary of the hydraulic capacity
at several locations along 8th Street, 1 lth Street, 14th Street, and Lower Kerper Subareas is
presented in Table 4.26. The additional capacity required for a proposed relief sewer to convey
the 2- and 10-year flood events is presented in the two right-hand columns of Table 4.26. Some
of the storm sewer segments evaluated do not provide the hydraulic capacity necessary for a 2-
or 10-year flood event.
4.6.4 Problem Areas
The flood hydrologic and hydraulic analyses provide the information needed for identification of
areas not in compliance with the City's drainage standards/criteria. The frequency and hazards
associated with particular flood events must be taken into account and the flood protection
required may vary from street to street. Consequently, the sizing of storm sewers must be
performed on a case-by-case basis, while considering the impact of each portion on the entire
system.
4.6.5 Development of Alternative Solutions
General alternatives focused on the entire Central Business District were not established. No
available sites for regional detention exist because of the topography and land use within the
Central Business District. Increasing the capacity of storm sewer inlets and pipes has the
potential for reducing street and property flooding within the Central Business District.
City of Dubuque, lowa Drainage Basin Master Plan
Bee Branch Drainage Basin 442 Fall 2001
BEE BRANCH DRAINAGE BASIN
4.6.5.1 Detention
Regional detention is not viable within the Central Business District.
4.6.5.2 Channel and Drainage Structure Improvements
The hydraulic capacities (pipe sizes) required for conveyance of the 2-year and 10-year flood
events within the Central Business District Drainage Subarea are reported in Table 4.26.
4.6,6 Recommendations for Improvement Alternatives
The sizing of individual storm sewers should be performed on a case-by-case basis. The
potential for flood damage posed by the various storm events should be weighed against the cost
of improvement.
4.6.7 Project Phasing
No project phasing is required for the Central Business District.
4.7 BEE BRANCH STORM SEWER TRUNK LINE
Figure 4.21 summarizes the problem areas in the Bee Branch Drainage Basin. The majority of
the problems are along the Bee Branch storm sewer trunk line and in the West 32nd Street
Subarea. Due to the large magnitude of construction, cost, and impact on the community,
improvements to the Bee Branch storm sewer trunk line are addressed separately. Because
expansion of detention storage in the upper subareas of the Bee Branch Drainage Basin is not
sufficient to eliminate flooding problems in the low-ly/ng, heavily developed north end of the
city; improvements must be made to the conveyance system in the lower subareas to reduce
flood damages.
City of Dubuque, lowa Drainage Basin Master Plan
Bee Branch Drainage Basin 4-43 Fall 2001
::3:
BEE BRANCH DRAi'NAGE BASIN'
4.7.1 Development of Alternative Solutions
The available improvement alternatives applicable to the Bee Branch Drainage Basin are
summarized in Table 4.27. A discussion of each alternative is given below.
Table 4.27
Bee Branch Drainage Basin
Flood Minimization Alternative Improvements
Public Education/Outreach
Prepare an educational program alerting
residents of the risk of flooding and methods
to minimize flood damage. Provide
subsidized flood insurance.
Expand Existing Detention Cell Capacity
Expand existing detention cell storage
volume, gate outlet capacity and/or pump
capacity.
· Floodplain Buyout · Create Upstream Detention
Purchase buildings located within the Purchase un-occupied property and
floodplain, construct detention cells.
Flood Proofing
Remove or minimize flood damage by
elevating homes and businesses, moving
electrical/mechanical devices to non-flooding
elevation, install flood panels at flooding
points (e.g. doors and windows).
Rehabilitate/Expand Capacity of Existing
Facilities
Repair damaged or increase conveyance
system where development has exceeded the
system's capacity
· Do Nothing · Open Channel Floodway
Accept continued occurrence of chronic Create an open channel conveyance system
flooding and storm water damages.
Relief Storm Sewer
Construct a parallel tnmk line storm sewer
system where development has exceeded the
capacity of the storm water conveyance
system
4.7.1.1 Nonstructural Alternatives
Education/Outreach
Public education programs can be instmmentai in reducing flood losses and future flood
casualities. Public outreach can include development of public programs to provide emergency
shelters and fncst aid during a flood event, emergency service to assist in evacuation of
residences, and educational programs intended to inform citizens of required safety practices
before, during and after a flood event.
City of Dubuque, Iowa Drainage Basin Master Plan
Bee Branch Drainage Basin 4-45 Fall 2001
BEE BRANCH DRA]rNAGE BASIN
Floodplain Buvout
A program to acquire and remove flood prone structures within the 100-year floodplain may be
feasible in reducing or eliminating flooding problems. This approach may be considered as a
major approach for clearing the entire area subject to flooding.
Flood Proof'ma[
Flood proofing of structures subject to flooding may be a cost effective alternative to reduce
flood damages. Installation of a variety of flood proofing systems would be required in order to
meet the varied needs of the structures located within the flood-prone areas. Flood proofing
facilities may range from structural modifications to reduce or ehminate damages from flooding
to educational programs that inform people how to protect their property or remain safe during a
flood event. Structural measures are usually implemented in commercial or industrial settings
where personnel are available to operate and maintain flood proofing devices. In residential
applications, flood proofing is usually limited to the relocation of vital residential systems such
as heating, cooling, water heaters and laundry areas to safe flooding areas. The relocation of
electrical services to areas above the anticipated water surface elevation is also required.
Frequently, casualties during flooding relate to structural failures of basement and foundation
walls. Public education is an effective means to inform people of these dangers.
Do Nothing Alternative
If the public is not concerned about the current frequency and magnitude of flooding problems in
the community, it may be a viable alternative to take no action.
4.7,1.2 Structural Alternatives
Expand Existina[ Detention Cell Capacity
Increasing the capacity of the 16th Street Detention Cell volume or the ability of the detention
cell outlet works to discharge flood flows could have a significant effect on flooding in the
Couler Valley area.
Create Upstream Detention
No opportunities exist for upstream detention along the alignment of the Bee Branch mink line.
However, potential upstream detention sites in subareas located in the upland portion of the Bee
Branch have a substantial impact on peak discharges in the trunk line. Maximizing the capacity
of the West 32nd Street Detention Cell provides the greatest potential for reducing peak
City of Dubuque, Iowa Drainage Basin Master Plan
Bee Branch Drainage Basin 4~16 Fall 2001
BEE BRANCH DRAINAGE BASIN
discharges in the Bee Branch storm sewer trunk line. Limited opportunities for upstream
detention exist in the other subareas.
Rehabilitate/Expand Capacity of Existing Facilities
Repair or replacement of storm water conveyance systems where development has exceeded the
system's capacity could decrease or eliminate flooding problems due to ponding in both the
upland and lowland areas. Smaller sewer systems feeding into the Bee Branch trunk line could
be improved to more effectively convey runoff to the trunk line and reduce localized flood
damages.
Open Channel Floodway
Conveyance of runoff through the flat, heavily developed Couler Valley area of Dubuque may
require capacity in excess of the Bee Branch trunk line. Construction of a large flood control
channel through the Couler Valley area would provide a significant increase in conveyance and
storage and could have a large impact on the flooding problem. This would require the purchase
of private and commercial property in the Couler Valley area and the relocation of individuals,
businesses, roads, and utilities.
Relief Storm Sewer
Construction of a relief storm sewer to expand the capacity of the Bee Branch storm sewer trunk
line would have a similar, although less dramatic, effect to that of a flood control channel. The
increase in conveyance would deliver water to the Mississippi River more quickly and decrease
flooding in the low-lying areas of the City. The benefit/cost ratio would be substantially lower
than that of the flood control channel; however, its consWaction would require purchase of fewer
properties and relocation of fewer households and businesses.
4.7.2 Recommendations for Improvement Alternatives
Analysis of the existing condition for the Bee Branch storm sewer trunk line indicates the major
flooding problems occur throughout the Bee Branch Drainage Basin for the 100-year storm (See
Figure 4-5). The selected alternative for the West 32nd Street Subarea, Alternative W32-5, has
the potential to reduce flooding in the Bee Branch Drainage Basin from West 32nd Street to
approximately 24th Street to approximately ½ to 1-½ feet of flow in the street. Figure 4-22
illustrates the reduction in flooding depths along the Bee Branch storm sewer trunk line with the
recommended Alternative W32-5 improvement. Below Windsor Avenue the impact of
increasing detention in the West 32nd Street Subarea is negligible for the 100-year flood. The
magnitude of the flooding indicates a significant increase in conveyance would be required to
affect a change below 24th Street. An alternative involving a dramatic increase in conveyance
city of Dubuque, Iowa Drainage Basin Master Plan
Bee Branch Drainage Basin 4-47 Fall 2001
BEE BRANCH DRAINAGE BASIN
would be required to reduce flooding downstream of 24th Street; therefore, available alternatives
addressing conveyance along the Bee Branch trunk line were investigated further. Specifically,
expansion of the 16th Street Detention Cell outlet works, a relief storm sewer and a flood control
channel were analyzed as potential solutions to flooding problems.
4.7.2.! Existing Conditions
The XP-SWiVIM model described in Section 4.5 was used to evaluate the Bee Branch storm
sewer trunk line. Existing conditions analyses involved modeling the existing storm water
system in the lower portion of the Bee Branch Drainage Basin to assess current flooding
problems and to provide a baseline condition for comparison with improvement alternatives. All
existing condition analyses assumed no improvements in the Bee Branch Drainage Basin. The
normal Mississippi River stage (elevation 594.3 feet) was used as the downstream boundary
condition for existing conditions analyses and represents the elevation which the Mississippi
River water surface equals or exceeds 50% of the time. At this stage, under current operating
procedures, the 16th Street Detention Cell gravity outlet gates are open and the three (3) pumps
are not activated.
The analyses show the existing facilities have capacity for flows associated with an event less
than the 10-year flood '(estimated at approximately the 3-year flood). Model results indicate 10-
year flooding depths ranging from 0.5 feet near 26th Street and Jackson Street to 3.4 feet near
19th and Elm Streets. Peak flooding depths for the 50-year range from 2 feet near 30th and
Jackson Streets to 4.8 feet near 22nd and Elm Streets. Peak flooding depths for the 100-year
range from 2.3 feet near 30th and Jackson Streets to 5.8 feet near 22nd and Elm Streets. A 100-
year interior rainfall event with a Mississippi River stage of 594.3 feet inundates approximately
1,170 homes and businesses.
An additional model analysis was performed to evaluate the effect of activating the pumps while
the gravity outlet gates are open. This analysis used the existing 100-year flows and the normal
Mississippi River stage as its boundary conditions. Activation of the pumps did not reduce peak
flooding depths or flow rates upstream of the 16th Street Detention Cell for these conditions but
did result in a 5-percent increase in peak outflow from the drainage basin. Based on these
results, operation of the pumps has little impact on flows and flooding depths while the gates are
open.
4.7.2.2 West 32nd Street Improvements
A second set of analyses was performed to evaluate the impact of the West 32nd Subarea
improvements on the Couler Valley area. The hydrographs associated with the most effective
West 32nd Street improvement, Alternative W32-5, were used as the boundary condition at the
City of Dubuque, Iowa Drainage Basin Master Plan
Bee Branch Drainage Basin 4-48 Fall 2001
BEE BRANCH DRAINAGE BASIN
West 32nd Street Detention Cell outlet. The remaining subbasin and subarea inflow hydrographs
were identical to those in the existing conditions analyses. The model was executed with the
normal Mississippi River stage and the 16th Street Detention Cell gravity outlet in operation, and
the pumps turned off. The 10-, 50-, and 100-year conditions were investigated.
Figure 4-22 shows the 100-year flooding depths in the Couler Valley area for Mississippi River
stage 594.3 feet with the West 32nd Street Subarea improvements implemented. When
compared with the existing flooding depths shown in Figure 4-5, the benefits of the
improvements are apparent. The improvements result in approximately 200 fewer properties or
970 homes and businesses inundated for the 100-year flood with Mississippi River stage 594.3
feet. In general, the West 32nd improvements substantially reduced peak flows and flooding
depths in the upper portion of the Washington Street Subarea but had little to no effect below the
Windsor Subarea outlet at 24th Street, the first major inflow downstream of West 32nd Street.
For 10-year conditions, flow in the storm sewer is siguiflcantly reduced in the upper portion of
the subarea, but there is little effect on street flooding. This suggests inlet improvements are
needed to alleviate flooding in the upper portion for a 10-year design. For 50-year conditions,
flooding depths are reduced by as much as 1.7 feet at 32nd and Saunders Streets in the upper
portion with less significant effects in the lower portions (for example, 0.3 feet at 22nd and Elm
Streets). Flooding depths are reduced by as much as 1.9 feet (at 32nd and Central Streets) in the
upper portion also with less significant effects in the lower portions (for example, 0.5 feet at 24th
and Washington Streets) for 100-year conditions. The results of the 50-year and 100-year
analyses show West 32nd Alternative W32-5 in combination with improvements to the Bee
Branch storm sewer system may significantly reduce or eliminate flooding in the downstream
roaches of the Bee Branch; therefore, subsequent investigations included Alternative W32-5 as
an upstream boundary condition.
4.7.2,3 Relief Sewer
Construction of a relief sewer in the lower reaches of the Bee Branch was then investigated to
supplement the capacity of the existing trunk line sewer. Because West 32nd Alternative W32-5
is shown to significantly impact flooding upstream of the Windsor Subarea outlet, trunk line
improvements were modeled beginning at 24th Street and extending downstream to the 16th
Street Detention Cell. A second conduit identical to the existing Bee Branch tnmk line was input
into the model effectively doubling the capacity. This geometry was evaluated with 10-, 50- and
100-year flows.
The Alternative W32-5 hydrograph was used as the upstream boundary condition since it
significantly reduces downstream flooding. Three (3) operating conditions at the 16th Street
Detention Cell were analyzed as downstream boundary conditions, as shown in Table 4.28.
City of Dubuque, Iowa Drainage Basin Master Plan
Bee Branch Drainage Basin 4-49 Fall 2001
BEE BRANCH DRAI'NAGE BAS]'N
Table 4.28
Bee Branch Drainage Basin
Downstream Boundary Conditions for Relief Sewer Alternative
1 Normal 594.3 594.3 Off Open N/A
2 Current Gate
Closure 598.5 598.5 Off Open N/A
Minimum
3 Water Pomp cell down in
Smface 598.5 591.5 On Closed anticipation of large
Elevation storm water
Note: discharges
1. WSEL- water surface elevation
Scenarios 2 and 3 in Table 4-28 include diversion of the 8th Street Subarea flows into the 16th
Street Detention Cell. Modeling of the three downstream boundary conditions show how the
proposed facilities will operate over a wider range of scenarios.
For a 10-year flood, the maximum system flooding depths occur at 24th and Elm Streets, with
depths of 1.6 feet, 1.9 feet, and 1.6 feet for the three downstream boundary condition scenarios,
respectively. Flooding depths at 24th and Elm Streets were reduced by a maximum of 1.5 feet
with the addition of a relief sewer. Flooding depths throughout the areas adjacent to the trunk
line were reduced to less than 1 foot. This result indicates a relief sewer may be a viable option
to achieve a 10-year level of protection. A potential relief sewer alignment is shown in Figure 4-
23. Estimated construction c~sts for a relief sewer with a 10-year flood capacity is
approximately $18.7 million.
For a 50-year flood, the maximum flooding depths also occur at 24th and Elm Streets with
depths of 2.5 feet, 2.7 feet, and 2.5 feet for the three downstream boundary condition scenarios,
respectively. While the relief sewer was shown to reduce flooding depths by a maximum of 1.4
feet, significant flow still exists in the street, including a depth of 3.2 feet at 22nd and Elm
Streets. Because of the street flooding, a relief sewer is not considered an effective option for a
50-year level of protection.
For a 100-year flood, only Scenario 1 was analyzed. It also showed a reduction of flooding
depth up to 1.4 feet, but significant flow was left in the street with depths remaining as high as
3.9 feet at 22nd and Elm Streets. Because the street flooding is excessive, a relief sewer is not
considered an effective alternative for a 100-year level of protection. In addition, Scenario 1
City of Dubuque, lowa
Bee Branch Drainage Basin 4-50 Drainage Basin Master Plan
Fall 2001
BEE BRANCH DRAINAGE BASIN
showed the relief sewer to be ineffective for the 100-year return period; therefore, no other
scenarios were investigated.
Further benefit may be gained throug~ improvements to tributary pipes feeding the Bee Branch
trunk line, assuming capacity of the storm sewer is expanded to handle the additional flows.
Increase in the capacity of inlets and pipes in theses systems could reduce or eliminate flood
damages due to localized pondlng. Limited information was available on the tributary systems;
therefore, they were not included in the analysis of the trunk line.
4.7,2.4 Flood Control Channel
A relief sewer is not an effective option for the 100-year return period; therefore, construction of
an open channel capable of conveying 100-year flood flows was investigated. Improvements
were modeled from 24th Street to the 16th Street Detention Cell, because the West 32nd Street
Alternative W32-5 effectively reduces flooding above 24th Street. The channel replaced the Bee
Branch trunk line in this reach, maintained the same invert as the trunk line, and was modeled as
an equivalent rectangular channel with a 100-foot bottom width. For the purposes of this study,
a preliminary alignment was chosen to assess the magnitude of homes and businesses impacted
by the channel. The exact alignment of the proposed channel requires further study. Figure 4-24
illustrates the preliminary alignment of Phase I (Point 1 to 2) and Phases I and II (Point 1 to 2 to
3). The West 32nd Street Alternative W32-5 hydrograph was used as the upstream boundary
condition in all of the analyses. Because there would be marginal difference in the cost of
constructing a channel for 10-, 50-, or 100-year protection, only the 100-year flows were
analyzed.
The first flood control channel analyses were performed to determine the size of channel
required to convey the flow assuming an unlimited outlet capacity at the 16th Street Detention
Cell. These analyses assumed the capacity of the gravity outlet would be increased to convey
flood flows without a rise in stage above that of the Mississippi River, and therefore resulted in
the minimum possible channel cross-section. This was accomplished by assuming a constant
water surface elevation in the 16th Street Detention Cell. By using a constant water surface
elevation, backwater effects from rising stages in the detention cell were eliminated and flow
was not limited by the capacity of the gravity outlet. These analyses were performed with two
different downstream boundary conditions at the 16th Street Detention Cell: constant water
surface elevations of 594.3 feet and 598.5 feet, the starting water surface elevations for Scenarios
1 and 2, respectively. Operating at a constant water surface elevation of 591.5 feet was not
considered, as this would be a gate closure condition and require a very large pump.
City of Dubuque, Iowa
Drainage Basin Master Plan
Bee Branch Drainage Basin 4-51 Fall 2001
BEE BRANCH DRAI'NAGE BASI'N
A sensitivity analysis examining the effect of improvements to storm sewer inlets and tributary
pipes was evaluated. The sizes of the tributary pipes in the model were increased so as to not
limit passage of flow from the street to the storm sewer. In this manner, the effect of inlets and
tributary pipes on the trunk line could be evaluated and a channel sized to carry the total street
and storm sewer flows.
The results of the first series of analyses indicates that for a constant water surface elevation of
594.3 feet in the 16th Street Detention Cell, a 10-foot-deep grass lined trapezoidal channel with a
60-foot bottom width and 3H:IV side slopYs would be required to convey flows associated with
the 100-year flood. For a constant water surface elevation of 598.5 feet in the 16th Street
Detention Cell, a 10-foot-deep grass-lined trapezoidal channel with a 66-foot bottom width and
3H:IV side slopes would be required.
While the improvement of the storm sewer inlets and tributary pipes decreased flooding depths,
the improvement had no impact on the flood control channel size. The analyses also showed the
16th Street Detention Cell was not the factor limiting the conveyance of the Bee Branch storm
sewer mink line. Reduction in flooding of the Couler Valley area therefore requires
modification to the Bee Branch storm sewer trunk line itself.
A second series of runs was performed to determine the effect of backwater from the 16th Street
Detention Cell. Improvements to tributary pipes were assumed to size the channel for the
maximum predicted peak discharges. These runs included the three (3) downstream boundary
conditions listed in Table 4.29.
Table 4.29
Bee Branch Drainage Basin
Downstream Boundary Conditions for Flood Control Channel Alternative
2 Current Gate
Closure 598.5 598.5 On Open N/A
Minimum
3 Water
Surface 598.5 591.5 On Closed N/A
Elevation
Note:
1. WSEL- water surface elevation
City of Dubuque, lowa Drainage Basin Master Plan
Bee Branch Drainage Basin 4-52 Fall 2001
BEE BRANCH DRAI'NAGE BASTN
The results of the second series of analyses show for Scenario 1, a slightly larger trapezoidal
channel with a 10-foot depth, 76-foot bottom width, and 3H:iV side slopes is required to convey
the 100-year flood flows. Scenarios 2 and 3 require a slightly deeper channel to contain the
flow: a 13.5-foot-deep trapezoidal channel with a 55-foot bottom width and 3H:IV side slopes.
In all three scenarios, flooding is significantly reduced with maximum flooding depths of 0.2
feet, 0.6 feet, and 0.1 feet for each of the three downstream boundary conditions, respectively.
A channel beginning downstream at the 16th Street Detention Cell and terminating at Garfield
Street was assumed as an initial phase, Phase I. Consequently, the existing storm sewer trunk
line was modeled from the West 32nd Street Detention Cell to Garfield Street with the flood
control channel constructed downstream. The results of this analysis for the Phase I flood
control channel are shown in Figure 4-25. The model results indicated the construction of the
initial phase of the flood control channel would only have significant impact on flooding for the
100-year storms downstream of Garfield Street. Water surface elevations were decreased by one
foot or more as far upstream as 25th Street; however, flooding depths remain two feet and higher
in these locations. This analysis demonstrates that partial construction of the project will not
provide adequate flood protection for the upper portion of the Bee Branch trunk line. Estimated
construction costs for the Phase I Flood Control Channel from the 16th Street Detention Cell to
Garfield Avenue are approximately $6.9 m/Ilion.
Further analysis was conducted to determine the effect of extending the flood control channel to
provide flood protection for the upper port/on of the Bee Branch storm sewer trunk line. The
original flood control channel was extended up to 24th Street for this analysis, Phase II. The
combined effect of the West 32nd Subarea improvements and construction of Phase I and II of
the Flood Control Channel for a Mississippi River stage of 594.3 feet is illustrated in Figure 4-
26. For the 100-year flood with Mississippi River stage 594.3 feet and tributary improvements,
the flood control channel in conjunction with the West 32nd Street improvements resulted in
fewer than 10 properties inundated. Construction costs for Phase I and ff of the Flood Control
Channel from the 16th Street Detention Cell to 24th Street are estimated at $17.1 million. The
demolition of the estimated 71 homes/businesses is included in the cost estimate.
Further benefit may be gained through tributary pipe improvements feeding the Bee Branch
trunk line. Increase in the capacity of inlets and pipes in theses systems could reduce or
eliminate flood damages due to localized ponding. Limited information is available on these
systems; therefore, they were not analyzed in detail.
City of Dubuque, Iowa
Drainage Basin Master Plan
Bee Branch Drainage Basin 4-53 Fall 200]
BEE BRANCH DRAINAGE BASIN
4.7.2.5 Additional Comments
An important consideration in the design of the flood control system is the effect of the
downstream boundary condition. It became apparent, through the course of these analyses, that
the worst-case downstream boundary condition is not the same for every return period.
Comparing the results of the three downstream boundary conditions modeled, it was found that
the critical condition for the 100-year flood is when the gates on the gravity outlet are closed.
Less volume of runoff is produced by the 10- and 50-year flood events, so the storage volume in
the 16th Street Detention Cell is not consumed as quickly when the gates are closed. Therefore,
the critical condition for the 10- and 50-year floods becomes the Mississippi River water surface
elevation of 598.5 feet with the gates open.
4.7.2.6 Summary
Analysis of the Bee Branch storm sewer trunk line indicates that implementation of West 32nd
Subarea Alternative W32-5 would have a significant impact on 100-year flood depths along the
Bee Branch from 32nd to 24th Streets, with a lesser impact further downstream. West 32nd
Subarea improvements result in approximately 200 properties removed from the floodplain at a
Mississippi River stage of 594.3 feet.
To further reduce flooding along the Bee Branch storm sewer trunk line, construction of a relief
storm sewer from 24th Street to the 16th Street Detention Cell was analyzed. It was determined
the relief sewer option was not viable for flood discharges in excess of the 10-year storm. It
would take an additional four (4) relief sewers equivalent in size to the existing Bee Branch trunk
line to eliminate the flooding depths produced by the 100-year event.
Construction of a flood control channel from the 16th Street Detention Cell to 24th Street was
then investigated. Improvements to tributary pipes were assumed to maximize the anticipated
100-year peak discharges used for sizing the channel. A grass-lined trapezoidal channel with
approximately a 10-foot depth, 76-foot bottom width, and 3H:IV side slopes was analyzed. The
flood control channel in conjunction with the West 32nd Street improvements was shown to
remove all but 4 of the 1,155 properties in the Washington Subarea from the 100-year floodplain
at a Mississippi River stage of 594.3 feet. Construction costs for Phases I and II of the flood
control channel from the 16th Street Detention Cell to 24th Street are estimated at $17.1 million.
4.7,3 Project Phasing
Improvements made to the Bee Branch storm sewer trunk line should progress from downstream
to upstream. If initial improvements were to be made upstream, resulting increases in peak
Ci~ofDubuqu~lowa
DrainageBas&MasterPlan
BeeBranch Drainage Bas~ 4-54
Fall2001
BEE BRANCH DRAINAGE BASI'N
discharges would be realized in the unimproved downstream reaches of the trunk line, increasing
flood damages.
City of Dubuque, Iowa Drainage Basin Master Plan
Bee Branch Drainage Basin 4-55 Fall 2001
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FI'NANCI'NG DRAI'NAGE 'rMPROVEMENTS AND OPERATI'ONS
5,0 FI'NANCI'NG DRAI'NAGE ?MPROVEMENTS AND OPERATI'ONS
Historically, many cities and towns in Iowa have considered municipal drainage a function of
public works and have funded drainage improvements similar to the methods used to finance
street and road improvements. Traditional tax revenues accruing to the General Fund have
historically been relied upon to fund the annual operation and maintenance expense of urban
drainage. General Obligation bonds have been the debt tools for funding major public projects
of which drainage is a component.
5.1 GENERAL FUND FINANCING
Drainage activities and improvements are supported by the municipality's General Fund or from
wastewater or sewage utility fees. Drainage projects are one of many "line items" in the
General Fund that are supported with the combined pool of general revenues from ad valorem
taxes, sales taxes and other revenue. Capital financing is typically accomplished through cash
transfers for small projects and general obligation bonds for major improvements. Operational
activities are usually funded with general revenues.
Advantages of the simple general revenue funding approach include:
· A broad base of financial support (all taxpayers pay), and
· Customers can deduct local taxes from Federal income taxes.
Disadvantages include:
· Competition for funding with other general services,
· A perceived lack of identity as a significant municipal utility function that must be
addressed with on-going efforts, and
· Inequities arising from tax liabilities not equated with contribution to drainage
problems.
With increasing attention given to the water quality aspects of urban drainage, especially with
respect to the EPA's Total Maximum Daily Loads (TMDLs) program, more municipalities are
moving this function into the water and/or wastewater enterprise fund, with some communities
establishing specific storm water enterprise funds. An enterprise fund is a self-supporting
component of municipal government that depends upon rates and fees, and frequently
development impact fees, to fund its activities. Water and wastewater utilities are examples of
municipal enterprises that are intended to be self-supporting. Enterprise funds typically finance
major capital improvements with revenue bonds that only require the approval of the local
governing body, such as the City Council, rather than a public vote, to approve the issuing of
City of Dubuque, Iowa Drainage Basin Master Plan
Financing Drainage Improvements and Operations 5-1 Fall 2001
F~NANCING DRATNAGE TMPROVEMENTS AND OPERATTONS
bonds. Being within an enterprise fund facilitates a sustainable storm water program because it
allows the utility to set rotes and charges on the basis of its actual direct and indirect costs of
providing this service.
As mentioned above, increased attention to urban drainage has created the demand for more
contemporary methods of funding drainage improvements. These newer methods of drainage
financing seek to: i) acknowledge the drainage problem as a formal utility function, and 2) seek
to place a greater financial burden for remediation or prevention of drainage and flooding
problems upon those activities contributing to the problem.
Numerous methods are available to finance drainage improvements and operations. As monies
for drainage projects become competitive with other city projects, the need to evaluate financing
alternatives is necessary. The remainder of this section reviews the methods that enterprise fund-
based storm water utilities can use to: (1) finance ongoing operation and maintenance activities;
(2) provide up-from financing for current and future capital projects; and (3) repay any
indebtedness that results from financing the capital projects.
5.2 FUNDTNG OPERATION AND MAINTENANCE ACTIVITIES
For storm water utilities that are either a stand-alone enterprise or are a component of the
water/wastewater enterprises, user charges are counted upon to fund ongoing activities. These
user charges are billed in a manner and frequency similar to that of water/wastewater charges,
such as monthly, bi-monthly, quarterly, or annual billing. Typically, the estimated annual
operation and maintenance (O&M) expenditures include labor costs, materials, machinery, and
some portion of General and Administrative (G&A) expenditures.
The basis for the drainage charge is frequently the volume of impervious area, such as rooftops,
sidewalks, driveways, streets, and other structures, in relation to total area. Impervious area is
generally indexed on a single-family residential equivalent basis (SFR). Impervious areas for
non-residential customers are often measured as a multiple of SFRs.
5.3 CAPITAL FUNDING
There is a wide range of sources of funds, including funds from public and private sources.
5.3.1 Pay-As-You-Go
Pay-As-You-Go financing is what its name implies. Improvements are made as sufficient
reserves are collected. This method is low risk, but considering that projects need to be
constructed and on-line in order to generate revenue, the funds are often not available when
City of Dubuque, lowa Drainage Basin Master Plan
Financing Drainage Improvements and Operations 5-2 Fall 2001
FINANCING DRAINAGE TMPROVEMENTS AND OPERATTONS
needed. However, for long-term capital improvement programs, it is often possible to phase the
improvements in a manner in which pay-as-you-go financing can comprise the majority of the
project's financing.
5.3.2 General Obligation Bonds
General obligation bonds are long-term municipal bonds that are backed by the full faith and
credit of the City. This means that the local government pledges to use ail of its taxing and other
revenue-raising powers to repay bondholders. General obligation bonds require a two-thirds
approval by voters. Since general obligation bonds have low risk due to excellent collateral,
interest rates are usually one half to one percent lower than other municipal bonds.
5.3.3 Revenue Bonds
Revenue bonds are backed by the revenue from the enterprise backing the project, including user
charges and, potentially, development impact fees. They also do not require a public referendum,
but only the approval of the city council. If defaulted, bondholders have rights to the project
revenues but not the project property. Revenue bonds are most typically used by water supply
and wastewater utilities.
Advantages of revenue bonds include:
· Credit analysis is relatively straight-forward compared to other types of bonds
· The primary beneficiaries pay for the facility
· Default on the issue does not burden local taxpayers
· Debt is not normally subject to a debt ceiling
· Improved financial management is promulgated and
· A voter referendum may not be required.
Disadvantages of revenue bonds include:
· Interest rate charges to the issuer are generally higher than rates charged for general
obligation bonds
· Revenue bond ordinance usually contain restrictive covenants which may constrain
operations
· The market for revenue bond debt is not as broad as for general obligation bonds.
City of Dubuque, lowa Drainage Basin Master Plan
Financing Drainage Improvements and Operations 5-3 Fall 2001
FINANCtNG DRAINAGE TMPROVEMENTS AND OPERA'I~ONS
5.3,4 Grants
Several grant programs are available for funding storm water-related activities. One of the most
common is the EPA's Non-point Source Implementation Grants, also known as Section 319
Grants~. These grants are intended to promote the use of Best Management Practices in
minimizing and/or mitigating nonpoint source water pollution, from a watershed perspective.
Section 319 Grants require a 40 percent cost share for studies and projects. The EPA has a
formula-based system for allocating their $200+ million dollar annual contribution to the States'
lead agencies (in Iowa, the Department of Natural Resources).
Other EPA grant programs include Water Quality Cooperative Agreements and Watershed
Assistance Grants. These programs can also be used for storm water-related facilities, but their
funding levels are minimal compared to the Section 319 program.
Other programs include:
· Department of Interior: Land and Water Conservation Fund Grants to States. As
indicated this program awards moneys to states for disbursement to individual
communities and projects. Though all states are eligible, the funds originate from
offshore oil leasing revenues and projects tend to focus on coastal areas.
· Department of Agriculture, Natural Resource Conservation Service: Watershed
Protection and Flood Prevention Program. Technical assistance and cost sharing
opportunities are available through this program, also known as the PL 565 Program
and the "Small Watershed Program". The level of cost sharing varies by project.
This program provides assistance for Best Management Practices in relatively small
watersheds (less than 250,000 acres).
· Department of Housing and Urban Development (HUD): Community Development
Block Grants. Though these grants are typically targeted for urban re-development,
they can also be used for infrastructure improvement, to the extent that these
improvements benefit the existing urban area. Most urban areas of 50,000 or more
typically receive some CDBG assistance. Annual grants range from $500,000 to
$750,000, with some cost-sharing involved. In some cases, municipal policies
dictate how these funds can be used.
Clean Water Act, Section 319(h).
City of Dubuque, Iowa Drainage Basin Master Plan
Financing Drainage Improvements and Operations 5-4 Fall 2001
FTNANCTNG DRAINAGE IMPROVEMENTS AND OPERATIONS
5.3.5 Developer Contributions
The need for a storm water facility addition in a community is often linked to new development.
Developers can also be obligated when existing downstream facilities will not handle flow
increases from upstream construction. Cities and counties must also frequently call on their
residents and current revenue sources to install oversized system that are not needed now but will
be if anticipated growth occurs. Existing property owners do not always feel they can or should
bear the cost of improvements, which are needed primarily to facilitate growth; therefore,
developer contributions enable communities to meet these kinds of demands on the system.
Charges are levied on new developments after the improvement is constructed, as a means of
balancing financial participation. The intent is to enable a community to achieve excess capacity
improvements in advance of growth, yet place an equitable portion of the cost on those
properties, which later develop and make use of the extra capacity built into the systems.
5.4 CAPZTAL RECOVERY
5.4.! Monthly User Charges
For purposes, of obtaining debt financing and meeting debt service coverage requirements,
monthly user charges must be set at a level that will generate sufficient annual revenue to cover
all O&M and debt service costs. More typically, total enterprise revenues must be anywhere
from 1.10 to 1.30 times higher than the sum of O&M and debt service costs.
S.4.2 Impact Fees
Development impact fees are a method of recovering capital costs that have been used to
construct new facilities for new customers. That is, drainage facilities constructed to
accommodate new growth should be paid for exclusively by the new residents benefiting from
these new facilities. Impact fees are used in most states for this purpose and have been upheld
by courts.
When rapid growth in the late 1970's and early 1980's hit many Iowa municipalities, a
noticeable number of municipalities implemented capital recovery (impact) fee programs for
new water and wastewater connections. Some implemented such fees for drainage as well.
These fees were targeted at making new growth "pay for itself." The intent of these up-front fees
were to gather cash for the purpose of partial or full financing of public capital improvements
attributable to new growth.
City of Dubuque, Iowa Drainage Basin Master Plan
Financing Drainage Impro~etnents and Operations 5-5 Fall 2001
FINANCING DRAINAGE IMPROVEMENTS AND OPERATIONS
Advantages of the capital recovery fee approach include:
· Partial or full funding of growth-induced drainage problems is borne by new
development,
· Specific funding becomes available for the sole use of drainage capital projects, and
· Incorporation into the mortgage financing, the interest is Federally tax deductible.
Disadvantages include:
· Raises the cost of new homes and lessens financing eligibility for home buyers,
· May re-locate some new development to nearby communities with lower or no fees,
· Takes time to accumulate enough fee revenue to make substantial contribution to new
project financing when needs may be immediate,
· Can create double-charge inequities arising from "growth" having paid once up-front
for drainage improvements and again over longer-term through taxes,
· Still leaves "existing" drainage and flooding problems subject to the difficulties of
General Fund financing mentioned above.
5.5 MUNICIPAL DRAINAGE UTILITIES
Iowa Legislature enacted a law (Iowa Code Sections 384.80-384.94) specifically authorizing the
creation of municipal drainage utilities. This Act allowed drainage utilities to be formed as an
enterprise fund function of municipal government on a par with the financial and operational
capabilities of municipal water/wastewater and electric utility funds. Typically, separate revenue
and (capital and operating) expense accounting is maintained with fund income arising from
drainage fee (rate) revenue and collection or transfers from other funds. Most common is a
periodic drainage fee (i.e. rate charge) that is usually made monthly and included on the
water/wastewater billing. This monthly drainage fee usually reflects a flat charge for single
family residential or a unit charge per amount of impervious cover for multi-family, commercial,
industrial, municipal, religious, and institutional land uses. The drainage fee levies should be
equitable, related to the extent of problem drainage caused by the land use, and produce a
targeted level of overall revenue recovery for the drainage utility. Equity includes reduction or
elimination of fees for low income and elderly customers. The income of a drainage utility can
also include the drainage capital recovery levy previously described.
City of Dubuque, lowa Drainage Basin Master Plan
Financing Drainage Improvements and Operations 5-6 Fall 2001
FINANCI'NG DRAZNAGE TMPROVEMENTS AND OPERATi'ONS
Advantages of the municipal drainage utility approach include:
· Provides continuing stream of income for on-going drainage improvements and
operational activities,
· Allows for the issuance of utility revenue bonds to fund capital improvements,
· With proper fee design, a reasonable charge can be levied that is equitable between
new development and longer-term residents and also equitable among differing land
uses, and
· Raises the chronic drainage issue to a higher profile level and better targets needed
actions.
Disadvantages include:
· tn gathering revenues as a monthly rate charge, this source of financing is not
deductible by rate-payers on Federal tax returns, and
· The City may incur slightly more administrative overhead due to the separate
enterprise fund accounting and potentially expanded drainage programs.
Municipal drainage utilities have been implemented by a number of cities in Iowa to fund
projects to mitigate existing drainage problems. A list of cities in Iowa is provided in Table 5.1.
Table 5.1
Municipal Drainage Utilities in Iowa
· DesMoines · Ames
· Sioux City · Burlington
· Cedar Rapids · Boone
· Garner
Base residential fees charged by municipal drainage utilities in Iowa were found to range from as
low as $1.50 per month for the City of Ames to as high as $4.60 per month for Des Moines. An
estimate of revenues that could potentially be generated by the City of Dubuque with a
comparable fee structure as some of the cities surveyed is presented in Table 5.2. As shown in
Table 5.2, annual revenues for the City of Dubuque with a comparable fee structure as the six
cities shown would range from about $415,600 to $2,124,300 per year. This type of revenue
would provide a means for the City to implement a number of projects for identified problem
areas over a period of five to ten years without the use of the general revenue fund or issuance of
capital improvement bonds.
City of Dubuque, Iowa Drainage Basin Master Plan
Financing Drainage Improvements and Operations 5-7 Fall 2001
FINANCZNG DRAZNAGE Tt4PROVEPlENTS AND OPERATt'ONS
Table 5.2
Estimated Annual Revenue for the City of Dubuque With Implementation of Municipal
Drainage Utility with Comparable Fee Structures
Des Moines 193,190 $4.60 $7,200,000.00 $2,124,300
Sioux City 82,970 $1.84 $1,100,000.00 $755,700
Cedar Rapids 114,560 $2.25 $970,000.00 $482,600
lAmes 48,415 $1.50 $353,000.00 $415,600
Burlington 26,855 $3.00 $234,000.00 $496,700
Boone 12,755 $1.95 $183,880.00 $821,700
Garner 2,915 $2.63 $55,000.00 $ i ,075,500
Notes:
1. Estimated number of customers for City of Dubuque is 57,000.
2. Estimated annual revenue determined by using the ratio of each city' s popalation with Dubuque's population, then
multiplying each city's muvicipal drainage utility annual revenue by the respective population ratio.
City of Dubuque, Iowa Drainage Basin Master Plan
Financing Drainage Improvements and Operations 5-8 Fall 2001
BIBLi'OGRAPHY
Chow, Ven Te. Open Channel Hydraulics. McGraw-Hill. New York, NY. (1988).
Dubuque, City of. Dubuque Area Geographic Information System (DAGIS). 2000.
Dubuque, City of. Aerial Photography. (1997).
Federal Emergency Management. Agency, Flood Insurance Rate Map, Dubuque County, Iowa
and Incorporated Areas, September 6, 1999.
Federal Emergency Management Agency, Flood Insurance Study, City of Dubuque, Iowa.
(1989).
Huff, Floyd A. and Angel, James R. Midwestern Climate Center and Illinois Water Survey,
Bulletin 71 (MCC Research Report 92-03), Rainfall Frequency Atlas of the Midwest.
(1992).
Hwang, Ned H.C. and Houghtalen, Robert J., Fundamentals of Hydraulic Engineering Systems.
Prentice Hall. Upper Saddle River, New Jersey. (1996)
Iowa Department of Transportation. Summary of Awarded Contract Prices for English and
Metric Items. (1999).
Iowa State University, Department of Construction and Civil Extension, Cable and Dolleing,
Iowa Construction Site Erosion Control Manual. September 1994.
U.S. Army Corps of Engineers. HEC-HMS Hydrologic Modeling System, User's Manual and
Technical Reference Manual (March 2000).
U.S. Army Corps of Engineers. HEC-RAS River Analysis System, User's Manual. (1995).
U.S. Department of Agriculture, Soil Conservation Service. Urban Hydrology for Small
Watersheds. Technical Release 55, Second Edition. (1986).
U.S. Department of Transportation, FHWA. Hydraulic Design of Highway Culverts. HI)S-5.
(1985).
U.S. Geological Survey, 7.5-Minute Series Topographic Maps, Scale 1:24,000, Contour Interval
5feet.
U.S. Department of Agriculture, Soil Conservation Service. Soil Survey of Dubuque County,
Iowa. (1985).
XP Software Pty. Ltd. XP-SWMM 2000, Storm water & Wastewater Management Model,
Version 7.5. (2000).
city of Dubuque, Iowa
Bibliography B-1 Fall 2001
Opinion of Probable
Construction Costs
Drainage Basin
Master Plan
City of Dubuque, Iowa
FaH 2001
I-DR
HDR Engineering, Inc.
TABLE OF CONTENTS
TABLE OF CONTENTS
NORTH FORK CA'r~'ISH CREEK DRAINAGE BASIN
Table A-1. Preliminary Construction Cost Estimate, Pennsylvania Detention (Excavation
Only), Expand Storage Upstream of Pennsylvania - Alternative 1
Table A-2. PmliminarD, Construction Cost Estimate, Pennsylvania Detention (Excavation
Only), Expand Storage Upstream of Pennsylvania & NW Arterial - Alternative 3
Table A-3. Preliminary Construction Cost Estimate, NW Arterial Detention, Expand Storage
Upstream of Pennsylvania - Alternative 1
Table A-4. Preliminary Construction Cost Estimate, NW Arterial Detention (Excavation Only),
Expand Storage Upstream of NW Arterial - Alternative 2
Table A-5. Preliminary Construction Cost Estimate, NW Arterial Detention, Expand Storage
Upstream of Pennsylvania & NW Arterial - Alternative 3
Table A-6. Preliminary Construction Cost Estimate, Rosemont between St. Celia and Winnie,
Expand Storage Upstream of Rosemont
Table A-7. Preliminary Construction Cost Estimate, Rosemont and Hillcrest, Expand Storage
Upstream of Rosemont
Table A-8.
Preliminary Construction Cost Estimate, Channel Improvements, Channel Reach:
Northwest Arterial to Rosemont, Expand Storage Upstream of Pennsylvania -
Alternative 1
Table A-9.
Preliminary Construction Cost Estimate, Channel Improvements, Channel Reach:
Northwest Arterial to Rosemont, Expand Storage Upstream of NW Axterial -
Alternative 2
Table A-10.
Preliminary Construction Cost Estimate, Channel Improvements, Channel Reach:
Northwest Arterial to Rosemont, Expand Storage Upstream of Pennsylvania & NW
Arterial ~ Alternative 3
City of Dubuque, Iowa Opinion of Probable Construction Costs
Table of Contents A-i Fall 2001
TABLE OF CONTENTS
Table A-11. Preliminary Construction Cost Estimate, Channel Improvements, Channel Reach:
Rosemont to Keyway, Expand Storage Upstream of Pennsylvania - Alternative 1
Table A-12. Preliminary Construction Cost Estimate, Channel Improvements, Channel Reach:
Rosemont to Keyway, Expand Storage Upstream of NW Arterial - Alternative 2
Table A-13.
Preliminary Construction Cost Estimate, Channel Improvements, Channel Reach:
Rosemont to Keyway, Expand Storage Upstream of Pennsylvania & NW Arterial -
Alternative 3
Table A-14. Preliminary Construction Cost Estimate, Channel Improvements, Channel Reach:
Keyway to Pennsylvania, Expand Storage Upstream of Pennsylvania - Alternative 1
Table A-15. Preliminary Construction Cost Estimate, Channel Improvements, Channel Reach:
Keyway to Pennsylvania, Expand Storage Upstream of NW Arterial - Alternative 2
Table A-16.
Preliminary Construction Cost Estimate, Channel Improvements, Channel Reach:
Keyway to Pennsylvania, Expand Storage Upstream of Pennsylvania & NW
Arterial - Alternative 3
Table A-17. Preliminary Construction Cost Estimate, Structure Improvements, Structure
Location: Rosemont, Expand Storage Upstream of Pennsylvania - Alternative 1
Table A-18. Preliminary Construction Cost Estimate, Structure Improvements, Structure
Location: Rosemont, Expand Storage Upstream of NW Arterial - Alternative 2
Table A-19.
Preliminary Construction Cost Estimate, Structure Improvements, Structure
Location: Rosemont, Expand Storage Upstream of Pennsylvania & NW Arterial -
Alternative 3
Table A-20. Preliminary Construction Cost Estimate, Structure Improvements, Structure
Location: Keyway, Expand Storage Upstream of Pennsylvania - Alternative 1
Table A-21. Preliminary Construction Cost Estimate, Structure Improvements, Structure
Location: Keyway, Expand Storage Upstream of NW Arterial - Alternative 2
Table A-22.
Preliminary Construction Cost Estimate, Structure Improvements, Structure
Location: Keyway, Expand Storage Upstream of Pennsylvania & NW Arterial -
Alternative 3
City of Dubuque, lowa Opinion of Probable Construction Costs
Table of Contents A-ii Fall 2001
TABLE OF CONTENTS
Table A-23.
Preliminary Construction Cost Estimate, Structure Improvements, Structure
Location: Pennsylvania/J.F. Kennedy, Expand Storage Upstream of Pennsylvania -
Alternative 1
Table A-24.
Preliminary Construction Cost Estimate, Structure Improvements, Structure
Location: Pennsylvania/J.F. Kennedy, Expand Storage Upstream of NW Arterial -
Alternative 2
Table A-25.
Preliminary Construction Cost Estimate, Structure Improvements, Structure
Location: Pennsylvania/J.F. Kennedy, Expand Storage Upstream of Pennsylvania
& NW Arterial - Alternative 3
Table A-26. Preliminary Construction Cost Estimate, Channel Cleating and Grubbing Reach:
Pennsylvania/J.F. Kennedy to University Optional for Alternative Nos. 1, 2 and 3
Table A-27. Prelim/nary Construction Cost Estimate, Structure Improvements, Structure
Location: Saratoga, Add an additional 36-inch Culvert
Table A-28. Preliminary Construction Cost Estimate, Structure Improvements, Structure
Location: Intersection of Rosemont and Hillcrest, Construct a 42" storm pipe
Table A-29.
Prelim/nary Construction Cost Estimate, Structure Improvements, Structure
Location: Rosemont between St. Celia and Winnie, Replace 84" RCP with 108"
RCP
Table A-30. Preliminary Construction Cost Estimate, North Fork Catfish Creek Drainage Basin:
RCB Culvert for North Fork Catfish Creek at University Avenue
BEE BRANCH DRAINAGE BASIN
Table A-31. Preliminary Construction Cost Estimate, West 32nd Street Drainage Basin
Upstream Improvements and Excavate West 32nd Street Detention ~ Alternative
W32-I
Table A-32. Preliminary Construction Cost Estimate, West 32nd Street Drainage Basin
Upstream Improvements and Build Berm at West 32nd Street Detention - Alt. W32-
2
City of Dubuque, Iowa Opinion of Probable Construction Costs
Table of Contents A-iii Fall 2001
TABLE OF CONTENTS
Table A-33.
Preliminary Construction Cost Estimate, West 32nd Street Drainage Basin
Upstream Improvements and Excavate West 32nd Street Detention - Alternative
W32-3
Table A-34.
Preliminary Construction Cost Estimate, West 32nd Street Drainage Basin
Upstream Improvements and Build Berm at West 32nd Street Detention - Alt. W32-
4
Table A-35.
Preliminary Construction Cost Estimate, West 32nd Street Drainage Basin
Upstream Improvements and Build Berm and Excavate at West 32nd Street
Detention - Alt. W32-5
Table A-36.
Table A-37.
Table A-38.
Table A-39.
Table A-40.
Table A-41.
Preliminary Construction Cost Estimate Kaufmann Avenue Subarea:
Grandview/Kaufmann Detention Cell
Preliminary Construction Cost Estimate Bee Branch Storm Sewer Trunkline
Improvements: Alternative 1 - Parallel Storm Sewer
Preliminary Construction Cost Estimate Bee Branch Storm Sewer Trunkline
Improvements: Alternative 2 - Flood Control Channel, Phase I - 16th Street
Detention Cell to Garfield Ave.
Preliminary Construction Cost Estimate Bee Branch Storm Sewer Trunkline
Improvements: Alternative 3 - Flood Control Channel, Phase II - 16th Street
Detention Cell to 24th Street
Preliminary Construction Cost Estimate Bee Branch Storm Sewer Trunkline
Improvements: Alternative 4 - 90-ft. x 10-ft. Box Culvert from 16th Street
Detention Cell to 24th Street
Preliminary Construction Cost Estimate Bee Branch Storm Sewer Trunkline
Improvements: Alternative 5 - Parallel Storm Sewer and 500 SF Channel
City of Dubuque, Iowa Opinion of Probable Construction Costs
Table of Contents A-iv Fall 2001
NORTH FORK CATFISH CREEK DRAINAGE BASIN
OPINION OF PROBABLE CONSTRUCTION COSTS
Table A-1. Preliminary Construction Cost Estimate, Pennsylvania Detention (Excavation Only)
Expand Storage Upstream of Pennsylvania - Alternative I
No. Description Unit Unit Cost* Quantity Item Cost
I Excavation CY $5.00 35,000 $175,000.00
2 Area Clearing & Grubbing AC $2,000.00 10 $20,000.00
3 Topsoil AC $3,000.00 10 $30,000.00
4 Seeding AC $3,000.00 10 $30,000.00
Subtotal $255,000.00
5 25% Contingency
$63,750.00
6 25% Administration, Legal, Engineering
$63,750.00
Tot~ $382,500.00
Table A~2. Preliminary Construction Cost Estimate, Pennsylvania Dctention (Exeavaffon Only)
Expand Storage Upstream of Pennsylvanla & NWArterial - Alternative 3
No. Description Unit Unit Cost* Quantity Item Cost
1 Excavation CY $5.00 70,000 $350,000.00
2 Area Clearing & Grabbing AC $2,000.00 13 $26,000.00
3 Topsoil AC $3,000.00 13 $39,000.00
4 Seeding AC $3,000.00 13 $39,000.00
Subtot~ $454,000.00
5 25% Contingency
$113,500.00
6 25% Administration, Legal, Engineering
$113,500.00
TotM $681,000.00
Table A-3. Preliminary Construction Cost Estimate, NgY Arterial Detention
Expand Storage Upstream of Pennsylvania - Alternative 1
No. Deschption Unit Unit Cost* Quantity Item Cost
1 Remove Outlet Constriction LS $2,500.00 t $2,500.00
SubtotaI $2,500.00
2 25% Contingency $625.00
3 25% Administration, Legal, Engineering $625.00
Total $3,750.00
* Unit costs based on 1999 dollars.
File: prelim_improv_cost_fall01 .xls A-1 12/13/2001
Table .4-4. Preliminary Construction Cost Estimate, NW Arterial Detention (Excavation Only)
Expand Storage Upstream of NW Arterial - Alternative 2
No. Description Unit Unit Cost* Quantity Item Cost
I Excavation CY $3.00 95,500 $286,500.00
2 Area Clearing & Grubbing AC $2,000.00 10 $20,000.00
3 Improved Drainage Inlet LS $25,000.00 1 $25,000.00
4 Topsoil AC $3,000.00 10 $30,000.00
5 Seeding AC $3,000.00 10 $30,000.00
Subtotal $391,500.00
6 25% Contingency
$97,875.00
7 25% Administration, Legal, Engineering
$97,875.00
Toml $587,250.00
Table A-5. Preliminary Construction Cost Estimate, NWArterial Detention
Expand Storage Upstream of Pennsylvania & NgF Arterlal - Alternative
No. Description Unit Unit Cost* Quantity Item Cost
1 Excavation CY $3.00 95,500 $286,500.00
2 Area Clearing & Grabbing AC $2,000.00 . 10 $20,000.00
3 Improved Drainage Inlet LS $25,000.00 1 $25,000.00
4 Topsoil AC $3,000.00 10 $30,000.00
5 Seeding AC $3,000.00 10 $30,000.00
Subtotal $391,500.00
6 25% Contingency
$97,875.00
7 25% Administration, Legal, Engineering
$97,875.00
$587,250.00
File: pmlim_improv_cost_fall01 .xls A-2 12/13/2001
Table A-t~ Preliminary Construction Cost Estimate, Rosemont between St. Celia and Winnie
Expand Storage Upstream of Rosemont
No. Description Unit Unit Cost* Quantity Item Cost
1 Excavation CY $3.00 15,500 $46,500.00
2 Area Cleating & Gn~bbing AC $2,000.00 I $1,000.00
4 Topsoil AC $3,000.00 1 $1,500.00
5 Seeding AC $3,000.00 I $1,500.00
Subtotal $50,500.00
6 25% Conringeney $12,625.00
7 25% Administration, Legal, Engineering $12,625.00
Total $75,750.00
· Unit cost based on 1999 dollars.
Table A-7. Preliminary Construction Cost Estimate, Rosemont and Hillcrest
Expand Storage Upstream of Rasemont
No. Description Unit Unit Cost* Quantity Item Cost
I Embankment CY $5.00 2,300 $11,500.00
2 Area Clearing & Grubbing AC $2,000.00 I $1,000.00
3 Topsoil AC $3,000.00 I $1,500.00
4 Seeding AC $3,000.00 1 $1,500.00
Subtotal $15,500.00
5 25% Contingency $3,875.00
6 25% Administration, Legal, Engineering $3,875.00
Total $23,250.00
Unit costs based on 1999 dollars.
File: prelim_improv_cost_fall01 .xls A-3 I2/13/2001
Table A-8. Preliminary Construction Cost Estimat~ Channel Improvements
Channel Reach: Northwest Arterial to Rosemont
Expand Storage Upstream of Pennsylvanla - Alternative 1
No. Description Unit Unit Cost* Quantity Item Cost
1 Channel Excavation CY $5.00 t,300 $6,500.00
2 Channel Clearing & Grabbing AC $5,000.00 0.63 $3,150.00
3 Topsoil AC $3,000.00 0.63 $1,890.00
4 Seeding AC $3,000.00 0.63 $1,890.00
Subtotal $13,430.00
5 25% Contingency $3,357.50
6 25% Administration, Legal, Engineering $3,357.50
Total $20, I45.00
Table A-9. Preliminary Construction Cost Estimate, Channel Improvements
Channel Reach: Northwest Arterial to Rosemont
Expand Storage Upstream of NW Arterial- Alternative 2
No. Description Unit Unit Cost* Quantity Item Cost
I Channel Excavation CY $5.00 1,300 $6,500.00
2 Channel Clearing & Grabbing AC $5,000.00 0.63 $3,150.00
3 Topsoil AC $3,000.00 0.63 $1,890.00
4 Seeding AC $3,000.00 0.63 $1,890.00
Subtotal $13,430.00
5 25% Contingency $3,357.50
6 25% Administration, Legal, Engineering $3,357.50
Total $20,145.00
* Unit costs based on 1999 dollars.
File: prelim_impmv_cost_fall01 .xls A-4 12/13/2001
Table A-10. Preliminary Construction Cost Estimate, Channel Improvements
Channel Reach: Northwest Arterial to Rosemont
Expand Storage Upstream of Pennsylvania & NW Arterial- Alternative 3
No. Description Unit Unit Cost* Quantity Item Cost
I Channel Excavation CY $5.00 1,300 $6,500.00
2 Channel Clearing & Grubbing AC $5,000.00 0.63 $3,150.00
3 Topsoil AC $3,000.00 0.63 $1,890.00
4 Seeding AC $3,000.00 0.63 $1,890.00
Subtotal $13,430.00
5 25% Contingency $3,357.50
6 25% Administration, Legal, Engineering $3,357.50
Total $20,145.00
Table A-II. Preliminary Construction Cost Estimate, Channel Improvements
Channel Reach: Rosemont to Keyway
Expand Storage Upstream of Pennsylvanio - Alternative 1
No. Description Unit Unit Cost* Quantity Item Cost
I Channel Excavation CY $5.00 26,000 $130,000.00
2 Channel Clearing & Grubbing AC $5,000.00 5.9 $29,700.00
3 Topsoil AC $3,000.00 5.9 $17,820.00
4 Seeding AC $3,000.00 5.9 $17,820.00
Subtotal $195,340.00
5 25% Contingency
6 25% Administration, Legal, Engineering
$48,835.00
$48,835.00
Total
* Unit costs based on 1999 dollars.
$293,010.00
File: prelim_improv_cost_fall01 .xls A-5 12/I 3/2001
Table A-12. Preliminary Construction Cost Estimat~ Channel Improvements
Channel Reach: Rosemont to Keyway
Expand Storage Upstream of NYY Arterial- Alternative 2
No. Description Unit Unit Cost* Quantity Item Cost
1 Channel Excavation CY $5.00 26,000 $130,000.00
2 Channel Clearing & Grabbing AC $5,000.00 5.9 $29,700.00
3 Topsoil AC $3,000.00 5.9 $17,820.00
4 Seeding AC $3,000.00 5.9 $17,820.00
Subtotal $195,340.00
5 25% Contingency $48,835.00
6 25% Administration, Legal, Engineering $48,835.00
Total $293,010.00
Table A-13. Preliminary Construcflon Cost Estimate, Channel lmprovements
Channel Reach: Rosemont to Keyway
Expand Storage Upstream of Pennsylvania & NIV Arterial - Alternative 3
No. Description Unit Unit Cost* Quantity Item Cost
I Channel Excavation CY $5.00 26,000 $130,000.00
2 Channel Clearing & Grubbing AC $5,000.00 5.9 $29,700.00
3 Topsoil AC $3,000.00 5.9 $17,820.00
4 Seeding AC $3,000.00 5.9 $t7,820.00
Subtotal $195,340.00
5 25% Contingency $48,835.00
6 25% Administration, Legal, Engineering $48,835.00
Total $293,010.00
* Unit costs based on 1999 dollars.
File: prelim_improv_c ost_fall01.xls A-6 12/13/2001
Table A-14. Preliminary Construction Cost Estimate, Channel Improvements
Channel Reach: Keyway to Pennsylvania
Expand Storage Upstream of Pennsylvania - Alternative 1
No. Description Unit Unit Cost Quantity Item Cost
I Channel Excavation CY $5.00 13,300 $66,500.00
2 Channel Clearing & Grabbing AC $5,000.00 1.4 $6,900.00
3 Topsoil AC $3,000.00 1.4 $4,140.00
4 Seeding AC $3,000.00 1.4 $4,140.00
Subtotal $81,680.00
5 25% Contingency $20,420.00
6 25% Administxation, Legal, Engineering $20,420.00
Total $122,520.00
Table A-15. Preliminary Construction Cost Estimat~ Channel Improvements
Channel Reach: Keyway to Pennsylvania
Expand Storage Upstream of NW Arterial - Alternative 2
No. Description Unit Unit Cost* Quantity Item Cost
Channel Excavation
2 Channel Clearing & Grubbing
3 Topsoil
4 Seeding
Subtotal
5 25% Contingency
6 25% Administration, Legal, Engineering
Total
CY $5.00 13,300
AC $5,000.00 1.4
AC $3,000.00 t.4
AC $3,000.00 1.4
* Unit costs based on 1999 dollars.
$66,500.00
$6,900.00
$4,140.00
$4,140.00
$81,680.00
$20,420.00
$20,420.00
$122,520.00
File: prelim_improv_cost_fall 0 l.xls A-7 12/13/2001
Table A-16. Prelimina~ Construction Cost Estimate, Channel Improvements
Cbannel Reach: Keyway to Pennsylvania
Expand Storage Upstream of Pennsylvania & NgV Arterial - Alternative 3
No. Description Unit Unit Cost* Quantity Item Cost
Channel Excavation
2 Channel Clearing & Grubbing
3 Topsoil
4 Seeding
Subtotal
5 25% Contingency
6 25% Adminish'ation, Legal, Engineering
Total
CY $5.00 13,300
AC $5,000.00 1.4
AC $3,000.00 1.4
AC $3,000.00 1.4
$66,500.00
$6,900.00
$4,140.00
$4,140.00
$81,680.00
$20,420.00
$20,420.00
$122,520.00
* Unit costs based on 1999 dollars.
File: prelim_improv_cost_fall01 .xls A-8 I2/I3/200I
Table A-17. Preliminary Construction Cost Estimat~ Structure Improvements
Structure Location: Rosemont
Expand Storage Upstream of Pennsylvania - Alternative 1
No. Description Unit Unit Cost* Quantity Item Cost
I Remove and Replace Roadway Surface SY $30.00 130 $3,900.00
2 Rehabilitation of Existing Structure LS $5,000.00 1 $5,000.00
3 Area Clearing and Grubbing AC $5,000.00 0.5 $2,300.00
4 2-72" RCP LF $182.00 154 $28,028.00
5 Concrete Apron EA $1,500.00 4 $6,000.00
6 Riprap SY $20.00 350 $7,000.00
7 Topsoil AC $3,000.00 0.2 $600.00
8 Seeding AC $3,000.00 0.2 $600.00
9 Channel Excavation CY $5.00 1,100 $5,500.00
I0
1t
Subtotal $58,928.00
25% Contingency $14,732.00
25% Administration, Legal, Engineering
$14,732.00
Toml $88,392.00
Table A-18. Preliminary Construction Cost Estimat6 Structure Improvements
Structure Location: Rosemont
Expand Storage Upstream of NW Arterial - Alternative 2
No. Description Unit Unit Cost* Quantity Item Cost
I Remove and Replace Roadway Surface SY $30.00 160 $4,800.00
2 Rehabilitation of Existing Structure LS $5,000.00 1 $5,000.00
3 Area Clearing and Gmbbing AC $5,000.00 0.4 $2,200.00
4 72" RCP LF $182.00 77 $14,014.00
5 Conarete Apron EA $1,500.00 2 $3,000.00
6 Riprap SY $20.00 350 $7,000.00
7 Topsoil AC $3,000.00 0.2 $600.00
8 Seeding AC $3,000.00 0.2 $600.00
9 Channel Excavation CY $5.00 800 $4,000.00
Subtotal $41,214.00
10 25% Contingency $10,303.50
11 25% Administration, Legal, Engineering
$I0,303.50
Toml $61,821.00
Unit costs based on 1999 dollars.
File: prelim_impr ov_cost_fall01 .xls A-9 12/13/2001
Table A-19. Preliminary Construction Cost Es~mate, Structure Improvements
Structure Location: Rosemont
Expand Storage Upstream of Pennsylvania & NW Arterial - Alternative 3
No. Description Unit Unit Cost* Quantity Item Cost
1 Remove and Replace Roadway Surface SY $30.00 160 $4,800.00
2 Rehabilitation of Existing Structure LS $5,000.00 I $5,000.00
3 Area Clearing and Grubbing AC $5,000.00 0.4 $2,200.00
4 72" RCP LF $182.00 77 $14,014.00
5 Concrete Apron EA $1,500.00 2 $3,000.00
5 Riprap SY $20.00 350 $7,000.00
6 Topsoil AC $3,000.00 0.2 $600.00
7 Seeding AC $3,000.00 0.2 $600.00
9 Channel Excavation CY $5.00 800 $4,000.00
10
11
Subtotal $41,214.00
25% Contingency $10,303.50
25% Administration, Legal, Engineering
$I0,303.50
Total $61,821.00
Table A-20. Preliminary Construction Cost Estimate, Structure Improvements
Structure Location: Keyway
Expand Storage Upstream of Pennsylvanio - Alternative I
No. Description Unit Unit Cost* Quantity Item Cost
I Remove and Replace Roadway Surface SY $30.00 200 $6,000.00
2 Remove Existing Structure LS $12,000.00 1 $12,000.00
3 Area Clearing and Grubbing AC $5,000.00 0.9 $4,450.00
4 3- 10'xS' RCB (Includes concrete apron) LF $530.00 297 $157,410.00
5 Riprap SY $20.00 800 $16,000.00
6 Topsoil AC $3,000.00 0.3 $900.00
7 Seeding AC $3,000.00 0.3 $900.00
8 Channel Excavation CY $5.00 4,700 $23,500.00
Subtotal $221,160.00
9 25% Contingency $55,290.00
10 25% Administration, Legal, Engineering
$55,290.00
Total $331,740.00
· Unit costs based on 1999 dollars.
File: prelim_improv_cost_fall01 .xls A-10 12/13/200I
Table A-2L Preliminary Constructlon Cost Estimate, Structure lmprovements
Structure Location: Keyway
Expand Storage Upstream of Nil/Arterial - Alternative 2
No. Description Unit Unit Cost* Quantity Item Cost
I Remove and Replace Roadway Surface SY $30.00 200 $6,000.00
2 Remove Existing Structure LS $12,000.00 1 $12,000.00
3 Area Clearing and Grubbing AC $5,000.00 0.9 $4,450.00
4 3- 10'xS' RCB (Includes concrete apron) LF $530.00 297 $157,410.00
5 Riprap SY $20.00 800 $16,000.00
6 Topsoil AC $3,000.00 0.3 $900.00
7 Seeding AC $3,000.00 0.3 $900.00
8 Channel Excavation CY $5.00 4,700 $23,500.00
9
10
Subtotal $221,160.00
25% Contingency $55,290.00
25% Administration, Legal, Engineering
$55,290.00
Total $331,740.00
Table A-22. Preliminary Construction Cost Estimate, Structure Improvements
Structure Location: Keyway
Expand Storage Upstream of Pennsylvanin & NW Arterial- Alternative 3
No. Description Unit Unit Cost* Quantity Item Cost
1 Remove and Replace Roadway Surface SY $30.00 200 $6,000.00
2 Remove Existing Structure LS $12,000.00 1 $12,000.00
3 Area Cleating and Grabbing AC $5,000.00 0.9 $4,450.00
4 3- 10'xS' RCB (Includes concrete apron) LF $530.00 297 $I57,410.00
5 Riprap SY $20.00 800 $16,000.00
6 Topsoil AC $3,000.00 0.3 $900.00
7 Seeding AC $3,000.00 0.3 $900.00
8 Channel Excavation CY $5.00 4,700 $23,500.00
Subtot~ $221,160.00
8 25% Contingency $55,290.00
9 25% Administration, Legal, Engineering
$55,290.00
Total $331,740.00
* Unit costs based on 1999 dollars.
File: prelim_improv_cost_ fall01 .xls A- 11 12/13/2001
Table A-23. Preliminary Construction Cost Estimate, Structure lmprovements
Structure Location: Pennsylvania/J.F. Kennedy
Expand Storage Upstream of Pennsylvanio - Alternative 1
No. Description Unit Unit Cost* Quantity Item Cost
1 Excavation CY $5.00 1,700 $8,500.00
2 Area Clearing and Grubbing AC $5,000.00 0.2 $1,000.00
3 Improved Inlet LS $20,000.00 1.0 $20,000.00
4 Ripmp SY $20.00 840 $16,800.00
5 Structural Wall LF $140.00 410 $57,400.00
6 Topsoil AC $3,000.00 0.2 $600.00
7 Seeding AC $3,000.00 0.2 $600.00
Subtotal $104,900.00
25% Contingency $26,225.00
25% Adm/nistrafion, Legal, Engineering
$26,225.00
Total $157,350.00
Table A-24. Preliminary Construction Cost Estimat~ Structure Improvements
Structure Location: Pennsylvania/J.F. Kennedy
Expand Storage Upstream of NW Arterial- Alternative 2
No. Description Unit Unit Cost* Quantity Item Cost
I Excavation CY $5.00 1,700 $8,500.00
2 Area Clearing and Grabbing AC $5,000.00 0.2 $1,000.00
3 Improved Inlet LS $20,000.00 1.0 $20,000.00
4 Riprap SY $20.00 840 $16,800.00
5 Structural Wall LF $140.00 410 $57,400.00
6 Topsoil AC $3,000.00 0.2 $600.00
7 Seeding AC $3,000.00 0.2 $600.00
8
9
Subtotal $104,900.00
25% Contingency $26,225.00
25% Administration, Legal, Engineering
Total
· Unit costs based on 1999 dollars.
$26,225.00
$157,350.00
File: prelim_imp rov_cosL fall01 .xls A-I2 12/13/2001
Table A-25. Preliminary Construction Cost Estimate, Structure Improvements
Structure Location: Pennsylvania/J.F. Kennedy
Expand Storage Upstream of Pennsylvania & NkV Arterial - Alternative 3
No. Description Unit Unit Cost* Quantity Item Cost
I Excavation CY $5.00 1,700 $8,500.00
2 Area Clearing and Grubbing AC $5,000.00 0.2 $1,000.00
3 Constrict Culvert Inle~ LS $20,000.00 1.0 $20,000.00
4 Riprap SY $20.00 840 $16,800.00
5 Structural Wall LF $140.00 410 $57,400.00
6 Topsoil AC $3,000.00 0.2 $600.00
7 Seeding AC $3,000.00 0.2 $600.00
Subtotal $t04,900.00
8 25% Contingency $26,225.00
9 25% Administration, Legal, Engineering $26,225.00
Total $157,350.00
Table A-26; Preliminary Construction Cost Estlmat~ Channel Clearing and Grubbing
Reach: Pennsylvania/J.F. Kennedy to University
Optional for Alternative Nos. 1, 2 and 3
No. Description Unit Unit Cost* Quantity Item Cost
1 Area Clearing and Grubbing (5000' x 50') AC $5,000.00 6.0 $30,000.00
2 Topsoil AC $3,000.00 6.0 $I8,000.00
3 Seeding AC $3,000.00 6.0 $18,000.00
Subtotal $66,000.00
4 25% Contingency $16,500.00
5 25% Administration, Legal, Engineering $16,500.00
Total $99,000.00
Unit costs based on 1999 dollars.
File: pr elim_improv_cost_fall01.xls A-13 12/13/2001
Table A-27. Preliminary Construction Cost Estimate, Structure Improvements
Structure Location: Saratoga
Add an additional 36-inch Culvert
No. Description Unit Unit Cost* Quantity Item Cost
1 Remove and Replace Roadway Surface SY $30.00 200 $6,000.00
2 Excavation for new pipe CT $10.00 50 $500.00
3 Area Clearing and Grabbing AC $5,000.00 0.t $500.00
4 Culvert, Concrete Roadway Pipe, 36" LF $60.00 100 $6,000.00
5 Granular Backfill CY $16.00 I0 $160.00
6 Ripmp SY $20.00 5 $100.00
7 Topsoil AC $3,000.00 0.1 $300.00
8 Seeding AC $3,000.00 0.1 $300.00
9 Channel Excavation CY $5.00 10 $50.00
Subtotal $13,910.00
10 25% Contingency $3,477.50
11 25% Administration, Legal, Engineering
$3,477.50
Total $20,865.00
Unit costs based on 1999 dollars.
Table A-28. Preliminary Construction Cost Estimate, Structure Improvements
Structure Location: Intersection of Rosemont and Hillcrest
Construct a 42" storm p~oe
No. Description Unit Unit Cost* Quantity Item Cost
I Remove and Replace Roadway Surface SY $30.00 650 $19,500.00
2 Excavation for new pipe CY $10.00 50 $500.00
3 Area Cleating and Grubbing AC $5,000.00 0.1 $500.00
4 Culvert, Concrete Roadway Pipe, 42" LF $100.00 375 $37,500.00
5 Granular Backfill CY $I6.00 30 $480.00
6 Riprap SY $20.00 5 $100.00
7 Topsoil AC $3,000.00 0.1 $300.00
8 Seeding AC $3,000.00 0.1 $300.00
9 Channel Excavation CY $5.00 10 $50.00
Subtotal $59,230.00
10 25% Contingency $14,807.50
11 25% Administration, Legal, Engineering
$14,807.50
Total $88,845.00
* Unit costs based on I999 dollars.
File: prelim_impmv_cost_ fall01 .xls A-14 12/13/2001
Table A-29. Preliminary Construction Cost Estimate, Structure Improvements
Structure Location: Rosemont be~aeen Sg Celia and Winnle
Replace 84" RCP with 108" RCP
No. Description Unit Unit Cost* Quantity Item Cost
1 Remove and Replace Roadway Surface SY $30.00 300 $9,000.00
2 Remove Existing Structure LS $12,000.00 I $12,000.00
3 Area Clearing and Grabbing AC $5,000.00 0. l $500.00
4 Culvert, RCP, 108" LF $500.00 100 $50,000.00
5 Granular Backfill CY $16.00 10 $160.00
6 Ripmp SY $20.00 5 $100.00
7 Topsoil AC $3,000.00 0.1 $300.00
8 Seeding AC $3,000.00 0.1 $300.00
9 Channel Excavation CY $5.00 10 $50.00
Subtotal $72,410.00
10 25% Contingency $18,102.50
11 25% Administration, Legal, Engineering
$18,102.50
Total $108,615.00
Unit costs based on 1999 dollars.
File: prelim_improv_cost_fall01 .xls A-15 12/13/2001
Table A-30. Preliminary Construction Cost Estimate, North Fork Catfish Creek Drainage Basin:
RCB Culvert for North Fork Catfish Creek at University Avenue
No. Description Unit Unit Cost* Quantity Item Cost
1 Pavement Removal and Replacement LF $180.00 30
2 Excavation LF $75.00 280
3 Utility Relocations LF $150.00 280
4 Bedding LF $100.00 280
5 Backfill LF $75.00 280
6 Seeding (50' ~ $2,500/AC) LF $3.00 280
7 Box Culvert -- 144 sq. ff. LF $850.00 280
8 Riprap - I 10' Ave. Channel Bottom Width - 2'
thick (136 lb/CF) LF $380.00 150
$5300.00
$21,000.00
$42,000.00
$28,000.00
$21,000.00
$840.00
$238,000.00
$57,000.00
Subtotal
$413,240.00
25% Contingency
$103,310.00
25% Administration, Legal, Engineering
$103,310.00
$619,860.00
Total
Note: Box culvert -- 2 CY/LF @ $425/CY
Description: Install Additional 12' x 12' x 280' RCB Culvert for North Fork Catfish Creek at University Ave.
Alignment of Proposed Box Culvert Runs Parallel to Existing 12' x 12' RCB Culvert
Unit costs based on 1999 dollars.
File: prelim_improv_cost_fall01 .xls A- 16 12/13/2001
BEE BRANCH DRAINAGE BASIN
OPINION OF PROBABLE CONSTRUCTION COSTS
Table A-31. Preliminary Construction Cost Estimate, West 32nd Street Drainage Basin
Upstream Improvements and Excavate West 32nd Street Detention - Alternative W32-1
No. Description Unit Unit Cost* Quantity Item Cost
Northwest Arterial 0F32_ ST_ l 5)
Modify Drainage Inlet LS $ 2,000.00
2 Subtotal Northwest ArteriaI Improvements
$2,000.00
$2,000.00
J.F. Kennedy OY32_ST_I 4)
3 Excavation CY $3.00 80,000 $240,000.00
4 Area Cleating & Grubbing AC $2,000.00 3.0 $6,000.00
5 Improved Drainage lnlet LS $15,000.00 I $15,000.00
6 Topsoil AC $3,000.00 3.0 $9,000.00
7 Seeding AC $3,000.00 3.0 $9,000.00
8 Subtotal J.F. Kennedy Improvements $279,000.00
Pedestrinn Crossing (W32_$T_13)
9 Embankment CY $5.00 9,000 $45,000.00
10 Area Clearing & Grubbing AC $2,000.00 I $2,000.00
11 Extend Drainage Pipe LF $I01.65 170.0 $17,280.50
12 Culvert Wingwall~teadwaI1 LS $2,600.00 1 $2,600.00
13 Topsoil AC $3,000.00 I $3,000.00
14 Seeding AC $3,000.00 I $3,000.00
I5 Subtotal Pedestrian Crossing Improvements $72,880.50
Detention Storage (W32_DET_4)
16 Embankment CY $5.00 70,000 $350,000.00
17 Area Clearing & Grubbing AC $2,000.00 3.5 $7,000.00
18 48-1N PCCP LF $170.00 270.0 $45,900.00
19 48-IN ControlIed Gate with Sensor LS $20,000.00 1 $20,000.00
20 Imake Structure (concrete riser) LS $60,000.00 1 $60,000.00
21 Outlet Structure (energy dissipater) LS $44,000.00 I $44,000.00
22 Control Building (8' x 8') LS $I5,000.00 1 $I5,000.00
23 Controller and Control Manhole LS $20,000.00 1 $20,000.00
24 Topsoil AC $3,000.00 3.5 $10,500.00
25 Seeding AC $3,000.00 3.5 $10,500.00
26 Subtotal D~tention Storage W32_DET_4 $582,900.00
West $2nd Street Deten~on
27 Remove Existing Drainage Outlet LS $10,000.00 I $10,000.00
28 Buyout of ResidentiaI Homes (15) LS $1,400,000.00 I $1,400,000.00
29 Excavation CY $5.00 146,000 $730,000.00
30 Area Clearing & Grubbing AC $2,000.00 12 $24,000.00
31 Automatic Controlled Gato ( 1T x 12') LS $I92,000.00 I $192,000.00
32 Monitoring Manhole with Modem LS $I0,000.00 4 $40,000.00
33 Outlet Weir Structure CY $350.00 I20 $42,000.00
34 Control Building (8' x 8') LS $15,000.00 1 $15,000.00
35 Controller and Control Manhole LS $20,000.00 1 $20,000.00
36 Topsoil AC $3,000.00 12 $36,000.00
37 Seeding AC $3,000.00 12 $36,000.00
38 Subtotal West 32nd Street Detention $2,545,000.00
39 Subtotal all Improvements - Alternative 1 $3,481,780.50
40 25% Contingency $870,445.13
41 25% Administration, Legal, Engineering $870,445.13
42 Total $5,222,670.75
* Unit costs based on 1999 dollars.
File: prelim_improv_cost_fall 01 .xls A47 12/13/2001
Table A-32. Preliminary Construction Cost Estimate, West 32nd Street Drainage Basin
Upstream Improvements and Build Berm at West $2nd Street Detention - Ala W32-2
No. Description Unit Unit Cost* Quantity Item Cost
Northwest Arterial (W32_ST_15)
1 Medi~ Drainage Inlet LS $ 2,000.00
2 Subtotal Nofdiwest Arterial Improvements
$2,000.00
$2,000.00
J.F. Kennedy (W32_$T_14)
3 Excavation CY $3.00 80,000 $240,000.00
4 Area Clearing & Crmbbing AC $2,000.00 3.0 $6,000.00
5 Improved Drainage Inlet LS $I5,000.00 I $15,000.00
6 Topsoil AC $3,000.00 3.0 $9,000.00
7 Seeding AC $3,000.00 3.0 $9,000.00
8 Subtotal J.F. Kennedy Improvements $279,000.00
Pedestrian Crossing (W32_ST_13)
9 Embankment CY $5.00 9,000 $45,000.00
I0 Area Cleating & Grubbing AC $2,000.00 1 $2,000.00
11 Extend Drainage Pipe LF $I01.65 170.0 $17,280.50
12 Culvert Wingwall/Headwall LS $2,600.00 1 $2,600.00
13 Topsoil AC $3,000.00 I $3,000.00
14 Seeding AC $3,000.00 1 $3,000.00
15 Subtotal Pedestrian Crossing Improvements $72,880.50
Detention Storage (W32_DET_4)
16 Embankment CY $5.00 70,000 $350,000.00
17 Area Clearing & Grabbing AC $2,000.00 3.5 $7,000.00
18 48-1N PCCP LF $170.00 270.0 $45,900.00
I9 48-IN Controlled Gate with Sensor LS $20,000.00 I $20,000.00
20 Intake Structure (concrete riser) LS $60,000.00 1 $60,000.00
21 Outlet Stmctore (energy dissipater) LS $44,000.00 1 $44,000.00
22 Control Building (8' x 8') LS $15,000.00 1 $15,000.00
23 Controller and Control Manhole LS $20,000.00 I $20,000.00
24 Topsoil AC $3,000.00 3.5 $10,500.00
25 Seeding AC $3,000.00 3.5 $10,500.00
26 Subtotal Detention Storage W32_DET_4 $582,900.00
West 32nd Street Detention
27 Remove Existing Drainage Outlet LS $ I0,000.00 1 $10,000.00
28 Buyout of Residential Homes (15) LS $1,400,000.00 I $1,400,000.00
29 Embankment CY $5.00 3,000 $15,000.00
30 Area Cleating & Grabbing AC $2,000.00 2 $4,000.00
3I Automatic Controlled Gate (12' x 12') LS $I92,000.00 I $192,000.00
32 Monitoring Manhole with Modem LS $10,000.00 4 $40,000.00
33 Outlet Weir Structure CY $350.00 120 $42,000.00
34 Control Building (8' x 8') LS $15,000.00 I $15,000.00
35 Controller and Control Manhole LS $20,000.00 1 $20,000.00
36 Topsoil AC $3,000.00 2 $6,000.00
37 Seeding AC $3,000.00 2 $6,000.00
38 Subtotal West 32nd Street Detention $1,750,000.00
39 Subtotal ail Improvements - Alternative 2 $2,686,780.50
40 25% Contingency $671,695.13
41 25% Administration, Legal, Engineering $671,695.13
42 Total $4,030,170.75
* Unit costs based on 1999 dollars.
File: prellm_improv_cost_fall01 .xls A- 18 12/I 3/2001
Table A-33. Preliminary Construction Cost Estimate, West 32nd Street Drainage Basin
Upstream Improvements and Eoccavate West 32nd Stre*q Detention - Alternative W$2-3
No. Description Unit Unit Cost* Quantity Item Cost
Northwest Arterial (W32_ST_15)
I Modify Drainage Inlet
2 Subtotal Northwest Arterial Improvements
Deten~on Storage OF32_DET_ 4)
LS $ 2,000.00 I $2,000.00
$2,000.00
3 Embankment CY $5.00 70,000 $350,000.00
4 Area Clearing & Grubbing AC $2,000.00 3.5 $7,000.00
5 48-IN PCCP LF $170.00 270.0 $45,900.00
6 48-IN Controlled Gate with Sensor LS $20,000.00 1 $20,000.00
7 Intake Structure (concrete riser) LS $60,000.00 1 $60,000.00
8 Outlet Structure (energy dissipater) LS $44,000.00 I $44,000.00
9 Control Building (8' x 8') LS $15~000.00 1 $15,000.00
10 Controller and Control Manhole LS $20,000.00 I $20,000.00
11 Topsoil AC $3,000.00 3.5 $10,500.00
12 Seeding AC $3,000.00 3.5 $10,500.00
13 Subtotal Detention Storage W32_DET_4 $582,900.00
26 Subtotal all lmprovementa - Alternative 3
27 25% Contingency
28 25% Administration, Legal, Engineering
29 Total
}Vest $2nd Street Detention
I4 Remove Existing Drainage Outlet LS $I0,000.00 I $10,000.00
15 Buyout of Residential Homes (15) LS $I,400,000.00 I $1,400,000.00
I6 Excavation CY $5.00 146,000 $730,000.00
17 Area Cleadng& Grabbing AC $2,000.00 12 $24,000.00
18 Automatic Controlled Gate (12'x 12') LS $192,000.00 1 $192,000.00
19 Monitoring Manhole with Modem LS $10,000.00 4 $40,000.00
20 Outlet Weir Structure CY $350.00 120 $42,000.00
21 Control Building (8' x 8') LS $15,000.00 1 $I5,000.00
22 ControIIer and Control Manhole LS $20,000.00 1 $20,000.00
23 Topsoil AC $3,000.00 12 $36,000.00
24 Seeding AC $3,000.00 12 $36,000.00
25 Subtotal West 32nd Street Detention $2,545,000.00
$3,129,900.00
$782,475.00
$782,475.00
$4,694,850.00
Unit costs based on 1999 doIIars.
File: prelim_imlxov_cost_fall01 .xls A-19 12/13/2001
Table A-34. Preliminary Consfrttcti~n Cost Estimate, West 32nd ~treet Drainage Basin
Upstream Improvements and Build Berm at West $2nd Street Detention - AIL IF32- 4
No. Description Unit Unit Cost* Quantity Item Cost
Northwest Arterial OF32_ST_15)
I Modi~ Drainage Inlet
2 Subtotal Norihwest Arterial Improvements
Deten~on Storage (IF32_DET_ 4)
LS $ 2,000.00 1 $2,000.00
$2,000.00
3 Embankment CY $5.00 70,000 $350,000.00
4 Area Clearing & Grubbing AC $2,000.00 3.5 $7,000.00
5 48-tN PCCP LF $170.00 270.0 $45,900.00
6 48-rlq Conic-oiled Gate with Sensor LS $20,000.00 1 $20,000.00
7 Intake Shmcture (concrete riser) LS $60,000.00 I $60,000.00
8 Outlet Structure (energ~ dissipater) LS $44,000.00 I $44,000.00
9 Control Building (8' x 8~ LS $I5,000.00 1 $15,000.00
10 Controller and Control Manhole LS $20,000.00 1 $20,000.00
11 Topsoil AC $3,000.00 3.5 $10,500.00
12 Seeding AC $3,000.00 3.5 $10,500.00
13 Subtotal Detention Storage W32_DET_4 $582,900.00
26 Subtotal all Improvements- Alternative 4
27 25% Contingency
28 25% Administration, Legal, Engineering
29 Total
West $2nd Street Detention
14 Remove Existing Drainage Outlet LS $10,000.00 1 $I0,000.00
15 Buyout of Residential Homes (I 5) LS $1,400,000.00 I $1,400,000.00
16 Embankment CY $5.00 3,000 $15,000.00
17 Area Clearing & Grubbing AC $2,000.00 2 $4,000.00
18 Automatic Controlled Gate (12' x 12~ LS $192,000.00 I $192,000.00
19 Monitoring Manhole with Modem LS $I0,000.00 4 $40,000.00
20 Outlet Weir Structure CY $350.00 I20 $42,000.00
21 Control Building (8' x 87 LS $15,000.00 1 $15,000.00
22 Conlroller and Control Manhole LS $20,000.00 1 $20,000.00
23 Topsoil AC $3,000.00 2 $6,000.00
24 Seeding AC $3,000.00 2 $6,000.00
25 Subtotal West 32nd Street Detention $1,750,000.00
$2,334,900.00
$583,725.00
$583,725.00
$3,502,350.00
· Unit costs based on 1999 dollars.
Table A-35. Preliminary Construction Cost Estimate, West 32nd Street Drainage Basin
Upstream Improvements, Build Berm & Excavate at West 32nd Street Detent'on - AIL IV32-5
No. Description Unit Unit Cost* Quantity Item Cost
Northwest Arterial (W3 2_ST_ 15)
I Modify Drainage Inlet
2 Subtotal Northwest Arterial Improvements
LS $ 2,000.00 I $2,000.00
$2,000.00
Detention Storage OV32_DET_4)
3 Embankment CY $5.00 70,000 $350,000.00
4 Area Clearing & Grubbing AC $2,000.00 3.5 $7,000.00
5 48-1N PCCP LF $170.00 270.0 $45,900.00
6 45-IN Controlled Gate with Sensor LS $20,000.00 I $20,000.00
7 Intake Structure (concrete riser) LS $60,000.00 I $60,000.00
8 Outlet Structure (energy dissipater) LS $44,000.00 I $44,000.00
9 Control Building (8' x 8') LS $15,000.00 I $15,000.00
10 Controller and Control ManhoIe LS $20,000.00 I $20,000.00
Ii Topsoil AC $3,000.00 3.5 $10,500.00
12 Seeding AC $3,000.00 3.5 $10,500.00
13 SubtotaI Detention Storage W32_DET_4 $582,900.00
14 Remove Existing Drainage Outlet LS $10,000.00 1 $10,000.00
I5 Buyout of Residential Homes (15) LS $1,400,000.00 1 $1,400,000.00
I6 Excavation CY $5.00 146,000 $730,000.00
17 Embankment CY $3.00 3,000 $9,000.00
18 Area Clearing & Grubbing AC $2,000.00 12 $24,000.00
19 Automatic Controlled Gate (12' x 12') LS $192,000.00 I $192,000.00
20 Monitoring Manhole with Modem LS $10,000.00 4 $40,000.00
21 Outlet Weir Structure CY $350.00 120 $42,000.00
22 Control Building (8' x 8') LS $15,000.00 I $15,000.00
23 Controller and Control Manhole LS $20,000.00 1 $20,000.00
24 Topsoil AC $3,000.00 12 $36,000.00
25 Seeding AC $3,000.00 12 $36,000.00
26 Subtotal West 32nd Street Detention $2,554,000.00
$3,138,900.00
$784,725.00
$784,725.00
$4,708,350.00
27 Subtotal ail Improvements - Alternative 5
28 25% Contingency
29 25% Administration, Legal, Engineering
30 Total
Unit costs based on 1999 dollars.
File: prelim_improv cost_£all01.xls A-21 12/I3/2001
Table A-36. Preliminary Construction Cost Estimate Kaufmann Avenue Subarea:
Grandview/Kaufmann Detention Cell
No. Description Unit Unit Cost* Quantity Item Cost
I Pavement Removal LF $20.00 550
2 Curb and Gutter LF $20.00 500
3 Excavation of Unusable Material CY $4.00 3,000
4 Excavation of Existing Sanitary Sewer LF $20.00 300
5 Utility Relocations LF $150.00 550
6 Bedding LF $25.00 150
7 48-inch RCP Storm Sewer LF $100.00 150
8 Backfill for Storm Sewer LF $45.00 150
9 Placement of Embankment CY $10.00 17,000
10 Traffic Warning Signals and Add'l Lighting LS $30,000.00 1
11 Seeding ACRE $2,500.00 2
Subtotal
25% Contingency
25% Administration, Legal, Engineering
Toml
Unit costs based on 1999 dollars.
Description: Construct detention cell at Grandview/Kaufmarm Connector road.
$I1,000.00
$10,000.00
$12,000.00
$6,000.00
$82,500.00
$3,750.00
$I5,000.00
$6,750.00
$170,000.00
$30,000.00
$5,000.00
$352,000.00
$88,000.00
$88,000.00
$528,000.00
File: prelim_improv_cost_fall01.xls A-22 12/13/2001
Table A-37. Preliminary Construction Cost Estimate
Bee Branch Storm Sewer Trunkline Improvements:
Alternative I - Parallel Storm Sewer
No. Description Unit Unit Cost* Quantity Item Cost
1 Pavement Removal and Replacement LF $180.00 5,300
2 Excavation LF $75.00 5,300
3 Bedding LF $100.00 5,300
4 Storm Sewer Trunk Line LF $1,800.00 5,300
5 Utility Relocations LF $150.00 5,300
6 Backfill LF $45.00 5,300
7 Seeding LF $2.50 5,300
Subtotal
25% Contingency
25% Administration, Legal, Engineering
Total
* Unit costs based on I999 dollars.
Alternative I with $ Sewer Lines:
$954,000.00
$397,500.00
$530,000.00
$9,540,000.00
$795,000.00
$238,500.00
$13,250.00
$12,468,250.00
$3,117,062.50
$3,117,062.50
$18,702,375.00
$93,511,875.00
Description: Additional Parallel Storm Sewer from 16th Street Detention Cell to 24th Street
to Supplement Existing Bee Branch Storm Sewer
File: prelim_improv_co st_fall0 t .xls A-23 12/13/2001
Table A-38. Preliminary Construction Cost Estimate
Bee Branch Storm Sewer Trunkline Improvements:
Alternative 2 - Flood Control Channel, Phase I- 16th Street Detention Cell to Garfield Ave.
No. Description Unit Unit Cost* Quantity Item Cost
I Pavement Removal LF $20.00 2,500 $50,000.00
2 Excavation LF $200.00 2,500 $500,000.00
3 Utility Relocations LF $150.00 2,500 $375,000.00
4 Relocate Railroad Track LF $50.00 2,000 $100,000.00
5 Bridge Construction - Roadway LS $700,000.00 1 $700,000.00
6 Bridge Construction - 2 Track Railroad LS $1,000,000.00 1 $1,000,000.00
7 Riprap - 72' Channel Bottom - 2' thick (l 36
lb/CF) LF $250.00 2,500 $625,000.00
8 Seeding (75' ~ $2,500/AC) LF $4.50 2,500 $11,250.00
9 Landscaping LS $70,000.00 I $70,000.00
10 Pedestrian/Bike Trail (10' wide) SF $2.00 25,000 $50,000.00
11 Paving LF $100.00 2,500 $250,000.00
Subtotal $3,731,250.00
25% Contingency
$932,812.50
25% Administration, Legal, Engineering
$932,812.50
12 Purchase/Relocate Residential Homes and
Businesses EACH
$I00,000.00 13
$1,300,000.00
$6,896,875.00
Total
* Unit costs based on 1999 dollars.
Note: Roadway Bridge -- 150' x 68' ~ $65/sq. ft.
Description: Replace Existing Bee Branch Storm Sewer System with Flood Control Channel.
Alignment of Proposed Flood Control Channel Extends from 16th St. Detention Cell to 24th St.
Phase II Only Includes the First 2500' of Flood Control Channel Starting at the 16th St. Detention Cell.
File: prelim_improv_eost_fall01 .xls A-24 12/13/2001
Table A-39. Preliminary Construction Cost Estimate
Bee Branch Storm Sewer TrunMine Improvements:
Alternative 3 - Flood Control Channel, Phases I & II- 16th Street Detention Ceil to 24th Street
No. Description Unit Unit Cost* Quantity Item Cost
1 Pavement Removal LF $20.00 4,500
2 Excavation LF $200.00 4,500
3 Utility Relocations LF $150.00 4,500
4 Relocate Railroad Track LF $50.00 2,000
5 Bridge Construction - Roadway LS $700,000.00 3
6 Bridge Construction - 2 Track Railroad LS $1,000,000.00 1
7 Riprap - 72' Channel Bottom - 2' thick (I 36
lb/CF) LF $250.00 4,500
8 Seeding (75' ~ $2,500/AC) LF $4.50 4,500
9 Landscaping LS $125,000.00 1
10 Pedestrian/Bike Trail (10' wide) SF $2.00 45,000
11 Paving LF $t00.00 4,500
Subtotal
25% Contingency
25% Administration, Legal, Engineering
12 Purchase/Relocate Resident/al Homes and
Businesses
EACH $100,000.00 71
Total
* Unit costs based on 1999 dollars.
I. Roadway Bridge -- 150' x 68' ~ $65/sq. fl.
2. Flood Control Channel Assumed to Begin at 16th St. Detention Cell and End at 24th St.
Description: Replace Existing Bee Branch Storm Sewer System with 4500' Flood Control Channel.
Alignment of Proposed Flood Control Channel Extends from 16th St. Detention Cell to 24th St.
$90,000.00
$900,000.00
$675,000.00
$I00,000.00
$2,100,000.00
$1,000,000.00
$1,I25,000.00
$20,250.00
$125,000.00
$90,000.00
$450,000.00
$6,675,250.00
$I,668,8t2.50
$1,668,812.50
$7,100,000.00
$17,112,875.00
File: prelim_improv_cost fall0I.xls A-25 12/13/2001
Table A-40. Preliminary Construction Cost Estimate
Bee Branch Storm Sewer Trunkline Improvements:
Alternative 4- 90-fl. x 10-fL Box Culvert from 16th Street Detention Cell to 24th Street
No. Desaripfion Unit Unit Cost* Quantity Item Cost
1 Pavement Removal and Replacement LF $180.00 4,500 $810,000.00
2 Excavation LF $180.00 4,500 $810,000.00
3 Utility Relocations LF $150.00 4,500 $675,000.00
4 Bedding LF $500.00 4,500 $2,250,000.00
5 Backfill LF $200.00 4,500 $900,000.00
6 Seeding LF $10.00 4,500 $45,000.00
7 Box Culvert -- 900 sq. f~. LF $6,500.00 4,500 $29,250,000.00
Subtotal $34,740,000.00
25% Contingency
25% Administration, Legal, Engineering
8 Purchase/Relocate Residential Homes and
Businesses EACH $100,000.00 50
$8,685,000.00
$8,685,000.00
$5,000,000.00
Total $57,110,000.00
* Unit costs based on 1999 dollars.
Note: Box culvert -- 14.8 CY/LF ~ $425/CY
Description: Replace Existing Bee Branch Storm Sewer System. Alignment of Proposed Box Culvert
Extends from 16th St. Detention Ceil to 24th St.
File: prelim_improv_cost_fall01 .xls A-26 12/13/2001
Table A-4L Preliminary Construction Cost Estimate
Bee Branch Storm Sewer TrunMine Improvements:
Alternative 5 - Parallel Storm Sewer and 500 SF Channel
No. Description Unit Unit Cost* Quantity Item Cost
Storm Sewer
I Pavement Removal and Replacement LF $180.00 5,300 $954,000.00
2 Excavation LF $75.00 5,300 $397,500.00
3 Bedding LF $100.00 5,300 $530,000.00
4 Storm Sewer Trunk Line LF $1,800.00 5,300 $9,540,000.00
5 Utility Relocations LF $150.00 5,300 $795,000.00
6 Backfill LF $45.00 5,300 $238,500.00
7 Seeding LF $2.50 5,300 $13,250.00
Flood Control Channel
1 Pavement Removal LF $11.00 4,500 $49,500.00
2 Excavation LF $111.00 4,500 $499,500.00
3 Utility Relocations LF $150.00 4,500 $675,000.00
4 Relocate Railroad Track LF $50.00 2,000 $I00,000.00
5 Bridge Construction - Roadway LS $412,000.00 3 $1,236,000.00
6 Bridge Construction - 2 Track Railroad LS $590,000.00 I $590,000.00
7 Riprap - 40' Channel Bottom - 2' thick (136
lb/CF) LF $140.00 4,500 $630,000.00
8 Seeding (75' ~ $2,500/AC) LF $2.50 4,500 $11,250.00
9 Landscaping LS $125,000.00 1 $125,000.00
10 Pedestrian/Bike TmiI (10' wide) SF $2.00 45,000 $90,000.00
11 Paving LF $100.00 4,500 $450,000.00
Subtotal $16,924,500.00
25% Contingency
$4,231,I25.00
25% Administration, Legal, Engineering
$4,231,125.00
12 Purchase/Relocate Residential Homes and
Businesses EACH $100,000.00 40
$4,000,000.00
$29,386,750.00
Total
* Unit costs based on 1999 dollars.
Description: Replace Existing Bee Branch Storm Sewer System with Parallel Storm Sewer
and Flood Control Channel. Alignments of Parallel Storm Sewer and Flood Control Channel extend
from 16th St. Detention Cell to 24th St.
File: pr elim_improv_cost_£all0 l.xls A-27 12/13/2001