Bee Branch Drainage Plan RFPMEMORANDUM
July 30, 2002
TO: The Honorable Mayor and City Council Members
FROM: Michael C. Van Milligen, City Manager
SUBJECT: Bee Branch Drainage Basin Master Plan Request for Proposals (RFP)
Assistant City Engineer Gus Psihoyos recommends authorization to solicit proposals
from qualified engineering firms to build a Drainage Basin Master Plan for the Bee
Branch watershed basin.
In December of 2001, the DBMP was formally adopted by the City Council. During the
Fiscal Year 2003 budget process, a capital improvement budget was recommended to
City Council based on the DBMP recommended improvements; however, because of
the opposition voiced by the residents, the portion of the proposed channel that was to
extend from Garfield Avenue to 24th and Elm Street was removed from the Fiscal Year
2003 budget. With the approval of the Fiscal Year 2003 CIP budget, funding was
established to hire an engineering firm to restudy the Bee Branch drainage basin. In
addition, Council authorized the use of a survey process to receive input from the
approximately 1,150 property owners and residents to gain a greater understanding of
the scope of the problem.
In December of 2001, at the recommendation of the Long-Range Planning Advisory
Commission, the City Council appointed Dr. Charles Winterwood (member of the Long-
Range Planning Advisory Commission) to chair the Citizen Advisory Committee for the
Bee Branch Creek Alignment Study. However, Dr. Winterwood's appointment was
subsequently tabled when the Fiscal Year 2003 budget was formally adopted. Having
expressed his interest in the Bee Branch Drainage Basin Master Plan, Dr. Winterwood
has been actively participating, providing input as a member the RFP Review
Committee. It is recommended that Dr. Charles Winterwood be appointed chairperson
of the Citizen Advisory Committee that will be formed as part of the Bee Branch
Drainage Basin Master Plan Project.
I concur with the recommendation and respectfully request Mayor and City Council
approval.
Michael C. Van Milligen
MCVM/jh
Attachment
cc: Barry Lindahl, Corporation Counsel
Cindy Steinhauser, Assistant City Manager
Gus Psihoyos, Assistant City Engineer
CITY OF DUBUQUE, IOWA
MEMORANDUM
July 30, 2002
TO: Michael C. Van Milligen, City Manager
FROM: Gus Psihoyos, Assistant City Engineer
SUBJECT: Bee Branch Drainage Basin Master Plan Request for Proposals (RFP)
INTRODUCTION
An RFP for the Bee Branch Drainage Basin Master Plan has been drafted and reviewed
by the proposal review committee.
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.
Increasing public safety and reducing property damage due to stormwater runoff are the
pdmary goals of the Stormwater Management Plan.
One of the elements of the Stormwater Management Plan is a Drainage Basin Master
Plan. 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 affects the drainage pattems 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.
Drainage problems in the Bee Branch watershed basin became evident on May 16,
1999. A severe thunderstorm moved through the Dubuque area producing between two
and a half (2.5) and five (5) inches of rainfall in a six-hour period, the latter would
indicate between a 50- and 75-year rainfall event.
In July of 2001, HDR Engineering (Omaha, NE) presented a preliminary Drainage Basin
Master Plan (DBMP) to the City of Dubuque City Council. It established the 100-year
flood plain for the Bee Branch watershed basin with over 1,150 homes and businesses
recognized as being within the floodplain limits and at risk of flood damage during a
100-year rainfall event. The DBMP identified several capital improvements that would
reduce the threat of flood damage. Table 1 lists the improvements recommended for
Bee Branch watershed basin and reveals the impact each improvement has on the
homes and businesses in the floodplain.
Table 1. Bee Branch Drains 9 Basin Improvements Recommended by HDR Engineering.
Homes &
Businesses
Improvemen Description Est. Cost Remaining Homes &
t In the Businesses
Floodplain Purchased
Upper Carter Build an earthen berm to create 182 $875,000
Detention acre-feet of storage.
Basin
Purchase 15 homes surrounding
W.32nd Street the existing basin and excavate
Detention within the basin to increase the $4,023,000 990(~) 15
Basin available storage 100% to 94 acre-
feet.
Grandview &
Kaufmann Build an earthen berm to create 44 $530,000
Detention acre-feet of storage.
Basin
Floodway 150' wide flood-way from the
from 16t~ St. existing 16th Street detention cell to $6,900,000 645(2) 17
to Garfield Garfield Ave. and Pine Street.
Floodway 150' wide flood-way from Garfield
from Garfield Ave. and Pine Street to 24th and $10,200,000 < 5(3) 53
to 24th Street. Elm Streets
85
TOTAL $22,528,000
1 .After the construction of the Carter Road detention cell and modifications to the existing
detention cell.
2.After the construction of the Carter Road detention cell, modifications to the existing W32nd Street
detention cell, and construction of the channel from 16th St. to Garfield.
3.After the construction of the Carter Road detention cell, modifications to the existing W32nd Street
detention cell, and construction of the channel from 16th St. to 24th and Elm.
In October, City staff presented the DBMP to the North End Neighborhood Association -
the neighborhood where the majority of the 1,150 homes and businesses are located.
The channel from 16th Street to 24th and Elm was presented. There were some
concerns expressed about relocating families. Building the channel from 16th Street to
24th and Elm would require the purchasing of approximately 70 homes/businesses.
In December of 2001, the DBMP was formally adopted by the City Council. During the
Fiscal Year 2003 budget process, a capital improvement budget was recommended to
City Council based on the DBMP recommended improvements.
In February, 2002, City staff presented the DBMP at a Washington Neighborhood
Council meeting. Many of the approximately 150 residents in attendance voiced
opposition to the portion of the DBMP that called for the removal of 70 homes.
Because of the opposition voiced by residents, the portion of the proposed channel that
was to extend from Garfield Avenue to 24th and Elm Street was removed from the Fiscal
Year 2003 budget. With the approval of the Fiscal Year 2003 CIP budget, funding was
established to hire an engineering firm to restudy the Bee Branch drainage basin. In
addition, Council authorized the use of a survey process to receive input from the
approximately 1,150 property owners and residents to gain a greater understanding of
the scope of the problem.
DISCUSSION
Several features will be incorporated into the Bee Branch Drainage Basin Master Plan
process to ensure that impacted residents are able to participate in the creation of the
drainage basin master plan for their neighborhoods.
Mr. Wayne Klosterman, President of the North End Neighborhood Association, and Mr.
Dan Shireman, President of the Washington Neighborhood Council, are serving as
members of the proposal review committee. The committee's objective is to review
proposals from consultants and to recommend to the City Council the engineering firm
whom the committee feels would be the best firm to prepare the Bee Branch Drainage
Basin Master Plan.
A significant prerequisite of the consulting firm will be its ability to work with impacted
residents. The Consultant must establish channels of communication that promote
input from the 1,150 impacted residents. The following shall be included in the project
scope: the formation of a Citizen Advisory Committee; the completion of a survey; public
meetings with neighborhood groups; and presentations to the City Council.
The Citizen Advisory Committee is to be assembled in such a manner that it generally
represents a cross-section of the impacted residents. The purpose of the Committee is
to help the Consultant produce a Drainage Basin Master Plan for the Bee Branch
watershed basin that consists of alternatives and improvements that are agreeable to
the impacted residents - arrive at a plan that the residents of the Bee Branch basin can
call their own. The Consultant must facilitate a consensus, enabling the committee to
recommend the adoption of the Bee Branch Drainage Basin Master Plan to the City
Council.
In December of 2001, at the recommendation of the Long-Range Planning Advisory
Commission, the City Council appointed Dr. Chades Winterwood (member of the Long-
Range Planning Advisory Commission) to chair the Citizen Advisory Committee for the
Bee Branch Creek Alignment Study. However, Dr. Winterwood's appointment was
subsequently tabled when the Fiscal Year 2003 budget was formally adopted. Having
expressed his interest in the Bee Branch Drainage Basin Master Plan, Dr. Winterwood
has been actively participating, providing input as a member of the RFP Review
Committee.
The schedule for the selection of a consulting firm is as follows:
RFP Sent to Firms August 7, 2002
Responses Due September 2, 2002
Committee To Establish Short List September 6, 2002
Interviews Conducted 3rd Week of September, 2002
Committee to Select Firm 4th Week of September, 2002
Committee to Recommend Firm to City Council October 7, 2002
With these dates as a guide, it is anticipated that the consultant would initiate the project
the first week of November. The project will require between nine and eighteen months
to complete.
RECOMMENDATION
I recommend that the City Council authorize the City Manager to solicit proposals from
qualified engineering firms to build a Drainage Basin Master Plan for the Bee Branch
watershed basin. In addition, I recommend that Dr. Charles Winterwood be appointed
chairperson of the Citizen Advisory Committee that will be formed as part of the Bee
Branch Drainage Basin Master Plan project.
BUDGET IMPACT
The engineering cost estimate for the Bee Branch Basin Master Plan Project is
$250,000. The project will be funded from a Fiscal Year 2003 General Fund
appropriation in the amount of $250,000.
ACTION REQUESTED
I respectfully request that the City Council authorize the City Manager to solicit
proposals from qualified engineering firms to develop a Drainage Basin Master Plan for
the Bee Branch watershed basin and that the City Council appoint Dr. Charles
Winterwood chairperson of the Citizen Advisory Committee to be formed as part of the
Bee Branch Drainage Basin Master Plan project.
CC:
Cindy Steinhauser, Assistant City Manager
Pauline Joyce, Administrative Services Manager
Ken TeKippe, Finance Director
Laura Carstens, Planning Services Manager
David Harris, Housing and Community Development Manager
Michael A. Koch, Public Works Director
Jerelyn O'Connor, Neighborhood Development Specialist
Susan Gwiasda, Public Information Officer
Deron Muehring, Civil Engineer
Dr. Charles Winterwood, Long-Range Planning Advisory Commission Member
Wayne Klosterman, North End Neighborhood Association President
Dan Shireman, Washington Neighborhood Council President
REQUEST FOR PROPOSALS
CONSULTING ENGINEERING SERVICES FOR THE
REVIEW/DEVELOPMENT OF A DRAINAGE BASIN MASTER PLAN FOR
THE BEE BRANCH DRAINAGE BASIN FOR THE CITY OF DUBUQUE (IA)
The City of Dubuque ("City") is seeking the services of a qualified consultant to assess
the Bee Branch watershed stormwater facilities. The Bee Branch Drainage Basin
Master Plan (BBMP) will investigate both structural and nonstructural flood mitigation
technologies.
INTRODUCTION
Dubuque is located on the Mississippi River in northeastern Iowa, adjacent to
Illinois and Wisconsin. The City is approximately 30 square miles in area, with a
population of nearly 60,000 persons. With an annual operating and capital
budget is nearly $100 million, funding a full range of services. More information
about the City organization can be found on the City's web site:
www.cityofdubuque.org.
Dubuque's terrain is varied, with steep hills and bluffs, and flat river valleys.
Rugged rock outcroppings dot the bluffs and many wooded areas are located
within the city limits. Located in the north-central portion of the city, the Bee
Branch watershed is approximately 7.1 square miles in area. It is bounded by W.
32nd Street to the north, Asbury Road and University Ave. to the south, NW
Arterial to the west, the Mississippi River to the east. Stormwater generally
drains from the west to the east: originating in the upland-bluff areas, it flows
down the steep slopes into the densely populated fiats where it is collected in the
"Bee Branch" storm sewer. The Bee Branch storm sewer originates
approximately 625-feet west of the W. 32"d Street and Saunders Street
intersection. Traveling in a southeasterly direction the sewer resides under
buildings, running diagonally with respect to the streets, until it reaches 28th and
Washington Street where the alignment follows Washington Street until 24th
Street. The storm sewer gradually increases from a 60-inch concrete pipe where
it originates to a 20-foot by 12-foot stone box where it outlets into the 16th Street
detention cell. Flow from the 16th Street detention cell outlets to the river either
through the flood wall or through the use of pumps when the Mississippi River is
high and the flood gates are closed.
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. Increasing public safety and reducing property damage due
to stormwater runoff are the primary goals of the Stormwater Management Plan.
7/19~2002
1
The Stormwater Management Plan consists of three elements:
A Drainage Basin Master Plan (DBMP) 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; and
An National Pollution Discharge Elimination System (NPDES) - Phase II
permit application that satisfies the requirements outlined in the Federal
Register.
Drainage problems in the Bee Branch watershed basin became evident on May
16, 1999. A severe thunderstorm moved through the Dubuque area producing
between two and a half (2.5) and five (5) inches of rainfall in a six hour period,
the later would indicate between a 50 and 75-year rainfall event.
In Juty of 2001, HDR Engineering (Omaha, NE) presented a preliminary
Drainage Basin Master Plan to the City of Dubuque City Council. It established
the 100-year flood plain for the Bee Branch watershed basin with over 1,150
homes and businesses recognized as being within the floodplain limits and at risk
of flood damage during a 100-year rainfall event. The DBMP identified several
capital improvements that would reduce the threat of flood damage. Table 1 lists
the Bee Branch watershed basin improvements recommended in the DBMP and
the impact the improvement has on the homes and businesses in the floodplain.
In October, City staff presented the DBMP to the North End Neighborhood
Association - the neighborhood where the majority of the 1,150 homes and
businesses are located. The channel from 16th Street to 24th and Elm was
presented. There was some concerns about relocating families. Building the
channel from 16th Street to 24th and Elm would require the purchasing of
approximately 70 homes/businesses.
In December of 2001, the DBMP was formally adopted by the City Council.
During the fiscal year 2003 budget process, a capital improvement budget was
recommended to City Council based on the DBMP recommended improvements.
In February, City staff presented the DBMP to Washington Neighborhood
Council. Many of the approximately 150 residents voiced strong opposition to
the portion of the DBMP that called for the removal of 70 homes - effectively
destroying "their neighborhood."
Because of the strong opposition by residents, the portion of th~ proposed
channel that was to extend from Garfield to 24th and Elm Street was removed
from the fiscal year 2003 budget. In addition, funding was established to hire an
engineering firm to prepare a drainage basin master plan specifically for the Bee
7/19/2002
2
Branch watershed basin and authorized the development of a survey process to
receive input from property owners and residents to gain a greater understanding
of the scope of the problem.
Table 1. Recommended W 32nd Street sub-basin improvements.
Homes &
Businesses
Improvemen Description Est. Cost Remaining Homes &
t In the Businesses
Floodplain Purchased
Upper Carter Build an earthen berm to create 182
Detention acre-feet of storage. $875,000
Basin
Purchase 15 homes surrounding
W.32*d Street the existing basin and excavate
Detention within the basin to increase the $4,023,000 990(~) 15
Basin available storage 100% to 94 acre-
feet.
Grandview &
Kaufmann Build an earthen berm to create 44 $530,000
Detention acre-feet of storage.
Basin
Floodway 150' wide flood-way from the
from 16th St. existing 16th Street detention cell to $6,900,000 645(2) 17
to Garfield Garfield Ave. and Pine Street.
Floodway 150' wide flood-way from Garfield
from Garfield Ave. and Pine Street to 24th and $10,200,000 < 5(3) 53
to 24th Street. Elm Streets
85
TOTAL $22,528,000
After the construction of the Carter Road detention cell and modifications to the existing W32nd
Street detention cell.
2. After the construction of the Carter Road detention cell, modifications to the existing W32nd
Street detention cell, and construction of the channel from 16t~ St. to Garfield.
3. After the construction of the Carter Road detention cell, modifications to the existing W32nd
Street detention cell, and construction of the channel from 16th St. to 24th and Elm.
II. OBJECTIVE
In general, the Bee Branch Master Plan will:
1)
2)
3)
Identify/verify drainage deficiencies in the Bee Branch watershed;
Establish structural and non-structural alternatives or combination of
alternatives that reduce the threat of flood damage; and
Work with impacted residents in the form of a citizens advisory committee
to ensure that the recommended alternatives are agreeable to the people
the proposed drainage improvements benefit.
7/19/2002
3
III.
SERVICES BY THE CITY
Information pertaining to the Bee Branch watershed compiled by HDR
Engineering (Omaha, NE) will be provided to the selected firm. Appendix A
includes an excerpt from the methodology section of the DBMP. Electronic files
associated with the computer modeling efforts will be made available.
The City of Dubuque has a geographical information system referred to as the
Dubuque Area Geographical Ihformation System, or DAGIS. Available
topographical mapping includes 2-foot contours, digital terrain models, parcels,
building outlines, edge of pavement, storm sewers, and aerial orthogonal photos.
IV.
INFORMATION TO BE INCLUDED IN PROPOSAl
To simplify the review process and to obtain the maximum degree of
comparability, the proposal will include the following information and will be
organized in the manner specified below.
Letter of Transmittal
Provide a letter of transmittal briefly outlining the consultant's understanding of
the work and the name, address, telephone number and fax number of the
consultant's primary contact person.
Profile of Firm
Provide and present the following information in a clear and concise format.
Consultants should feel free to present material to ensure that the City is fully
aware of their experience and expertise in this type of project.
A. Provide the Firm's official name, address, and principal offices
Provide references illustrating the firm's experience preparing drainage
basin master plans, working with impacted residents, and building
consensus with a citizen group for municipalities having similar physical,
social, and economic characteristics as Dubuque. For each reference list:
1)
2)
3)
4)
Project name and location;
Contact person and telephone number;
Cost of work (actual cost vs. initial estimated cost); and
Time required to complete the project
Provide abbreviated resumes (one to two pages each) of the key
personnel who will be working on the project, describing their education,
specialized and technical competence, and experience in relation to the
work referenced in part B above.
D. Specify the Firm's ability to integrate this project into their work schedule.
7/19/2002
Although the City attempted to identify the work and services required, this
4
should not constrain the scope the Consultant believes to be necessary to
meet the City's objective. Include any ideas to improve the development
of the plan and recommend work not identified in this RFP considered
essential by the firm.
Include a project schedule outlining the time period and estimated
completion date of the proposed scope of work. This should include a
schedule for and description of all deliverable products throughout the
period.
The proposal will specify anticipated City resources in terms of personnel,
facilities or equipment to be utilized by the consultant during the project
contract period.
SCOPE OF WORK AND SERVICES
The Consultant will carry out the following tasks. Responders may propose
additional tasks that would help reach the project goal.
Public involvement and project management
The Consultant must establishing channels of communication that promote input
from the 1,150 impacted residents. The following shall be included in the project
scope: the formation of a Citizen Advisory Committee; the completion of a
survey, public meetings with neighborhood groups; and presentations to the City
Council.
The Citizen Advisory Committee is to be assembled in such a manner that it
faithfully represents a cross section of the impacted residents. The purpose of
the committee is to help the Consultant produce a Drainage Basin Master Plan
for the Bee Branch watershed basin that consists of alternatives and
improvements that are agreeable to the impacted residents. The Consultant
must facilitate a committee consensus, enabling the committee to make a
recommendation to the City Council.
The City Council has directed a member of the Long-Range Planning Advisory
Commission to chair the Citizen Advisory Committee meetings. However, it will
be the Consultant's responsibility to prepare information for all required meetings
and public hearings. The necessary information may include but is not limited to:
invitation letters; hearing handouts; aerial displays; and exhibits including maps,
drawings, photos, and slides. It will be the Consultant's responsibility to set the
agenda for all meetings with Citizen Advisory Committee.
Verify existing drainage conditions
Aside from the gathering of physical data, this stage will include gathering input
from the residents who make up the 1,150 at risk homes and businesses. This
will require a survey and public meetings with impacted residents. The survey
must be a scientific survey that statistically represents the group. If the
7/19t2002
5
VII.
consultant prefers that the City undertake a portion of the fact finding survey
through the use of a local organization proficient at such a task, it should be
indicated in the proposal.
Establish viable alternatives
Several alternatives have been identified in the DBMP previously adopted by the
City Council. The consultant should utilize the improvements identified in the
DBMP as they see fit. As stated previously, the consultant must work ctosely with
the Citizen Advisory Committee to alternatives/improvements that are agreeable
to the people they benefit.
Establish the recommended alternatives
The consultant must present the gamut of alternatives to, and work closely with,
the Citizen Advisory Committee and City staff to formulate the alternatives that
will be recommended as the Bee Branch Master Plan presented to City Council.
EVALUATION CRITERIA
Proposals will be screened to ensure that they meet the minimum requirements
of the proposal format. A review of qualifying proposals will identify potential
firms which most closely meet the needs of the City of Dubuque. Proposals will
be evaluated by the selection committee based upon the following (not
necessarily listed in order of importance):
A, Qualifications and experience of the firm-reference checks, achievements
and completion of similar projects for municipalities with characteristics
similar to Dubuque.
B. Project design team-qualifications and experience of the principal
consulting staff proposed to work on the project; variety and application of
various disciplines within the team, and availability and qualifications of
any subcontracting staff.
C. Grasp of the project requirements-the firm's analysis, preparation and
level of interest.
D. Design approach/methodology in completing the scope of work and
services-technical alternatives, creativity and problem solving ability.
E. ,' Responsiveness-compatibility between consultants and the City of
Dubuque, general attitude, ability to communicate.
F. Qualifications/experience of the firm working with large groups of private
citizens, gathering input and building consensus,
G. Local economic impact-ability to incorporate local firms.
H. Schedule evaluation-time required to complete the project.
I. Proposed cost to complete the project.
The RFP committee will rank the responsive consultants and compile a short list
of firms. Consultants remaining after the initial screening will be contacted and
invited to interview during the 3rd week of September. The purpose of the
7/19/2002
6
VIII.
IX.¸
interview will be to allow the consultant to make a presentation before the
committee and allow members of the committee to ask questions of the
consultants. Firms will be ranked based on the final interview and overall
responsiveness to the RFP. The committee will make its recommendation to City
Council at the October 7, 2002 City Council Meeting.
The City of Dubuque is an Equal Employment Opportunity Employer.
FEES AND COMPENSATION
Separate the Fees and Compensation proposal (separate enclosure) from the
other portion of the RFP submittal, initial screening will be done by the selection
committee without the benefit of knowing the consultant's proposed fee for
services. A contract will be negotiated after the selection process has been
completed.
Taxes
The City of Dubuque is exempt from all State sales tax. Do not include sales tax
in the Firm's proposal price. Tax exemption certificates will be supplied upon
request.
Contract Documents
The Contract Documents will consist of the Advertisement of Proposals, the
Request for Proposal, Addendums to the Proposal, Responses to Follow-up
Questions and the signed Contract. These Documents will be on file with the
City Clerk.
SUBMISSION REQUIREMENTS
Proposals are to be signed by an officer of the firm authorized to bind the
submitter to its provisions. Proposals are to contain a statement indicating the
period during which the proposal will remain valid. A period of not less than
ninety (90) days is required. The proposal submitted by the firm shall become an
integral part of the contract between the City and the Firm and representations,
covenants, and conditions therein contained shall be binding upon the person,
firm or corporation executing the same. Failure to manually sign proposal will
disqualify it.
An original plus 10 copies of the proposal must be received in the office of the
City of Dubuque's Engineering Division by 5:00 p.m. CDT on September 4, 2002.
The address is:
City of Dubuque (Engineering)
C/O Gus Psihoyos, Assistant City Engineer
50 West 13th Street
Dubuque, Iowa 52001-4864
7/19/2002
7
Each firm assumes full responsibility for delivery and deposit of the completed
proposal package on or before the deadline. The City of Dubuque is not
responsible for any loss or delay with respect to delivery of the proposals.
The City of Dubuque is not liable for any cost incurred during the preparation of
proposals by any firms prior to the execution of an agreement or contract. Nor
shall the City of Dubuque be liable for any costs incurred by the firms that are not
specified in contract documents.
Appendix B outlines the insurance requirements for professional services.
All questions and correspondence regarding this RFP should be directed to Gus
Psihoyos (563-589-4275) or Deron Muehring (563-589-4276) from the City of
Dubuque Engineering Division, or by fax at (563) 589 - 4205.
7/19/2002
8
APPENDIX A
9
METHODOLOGIES
2,0 METHODOLOGIES
Flood hydrology models were developed for each individual drainage basin, incorporating the
unique characte~stics of each basin to simulate r~moff for specific stm,'rn events. Stream
hydraulic models were developed for ~e se~ents ~ciuded ~ ~is study inco~oraiflng ~e
channel and ~oodplMn geomet~ de~ved ~om sepal topo~ap~c maps, rou~ness
ch~cte~stics of cha~m~I bz~ks ~d ~oodplMns ~d ~e numerous b~dges ~d culve~s thru cross
the s~eams ~d affec~ ~ood levels. ~e following sections desc~be the methodolo~es used in
~s study.
2.1 PHYSICAL CHARACTERISTICS
2.1,1 Topography
Topo~aphy 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 oft. he drainage area.
Ail other parameters considered equal, as the slope of a drainage area increases, the faster the
wazer travels to the outlet point. Although there can be a great deal of variation in slope
magx/tude 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.
Drainage areas within the City typically have a much steeper over/and slope than charmeI slope.
Eievation measurements and slope calculations were performed using the Dubuque Area
Geographic ~formation System (DAGIS). The DAGIS included a digital terrain model 0DTM)
consisting of spot elevations and brealdines generated from aerial survey and ground control
data. Two-foot elevation contour lines created from the DTM were also included in the DAGIS
database. T'ne DTM was used to produce two additional tm-rain models for use in the analysis.
A trian~!ar 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 chamneI hydraulic models. A di~taI elevation model (DEM), a grid compr/sed of
i0-meter cells, was created 5'om the TIN for use in delineating drainage areas, es~naating
hydroio~c parameters, and creating hydrolo~c models.
METHODOLOGIES
2.1.2 Soil Types
The types of soils present in a drainage area have a signiiieant impact on uhe amount of runoff a
given storm will produce. This impact is influenced primarily by the. ir~lmation characteristics
of the soil.
Infonm, ation on the soil ~%ypes and characteristics for each drainage area was compiled by
developing a digital soils database in OlS. Soil survey SSL'-RGO and SATSGO databases
developed by the Natural Resources Conservation Service (bFR. CS) 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 ~oup '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 eacld 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 tt~ougj~ storm sewer systems and natural chanmels. The effect land use has
on water quantity is generally linked to the amount of impervious area for a particulm,- 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 chan2el due to lower in~21tration losses into the ~ound and lower s'ozface
rou~mess of the land. Ln general, an area with a high percentage of impervious area will have a
quicker time to peak and a 1~Jgher peak, than a sLrnilar area with a lower percentage impervious.
The scope of this project was to model stprm water quantity for uItkmate 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 personnd. The landuse categories witl-2n the drainage basins are
shown in Table 2.1.
METHODOLOGIES
Table 2.1
Drainage Basin Land Use Groups
Land L'se Group ~ : 'D'escripti6n
ST Streets
CO Commercial
IndusUial
Institutional
HD High Density Res/dent/al
Medium Density Residential
LD Low Density Residential
AG A~mdculmrat
OP
Op. enSpace and Grass
2.3 HYDROLOGIC MODEL
The U.S. Army Co~s of En~neers (USACE) Hydrolo~c Engineering Center (HEC) Hydrolog/c
Modeling System (HEC?L.MS) was selected to model the drainage areas in the city of Dubuque.
HEC-HMS simulates precipitation-runoff processes of dendritic drainage systems. HEC-H2MS
computes runoff volume by computing the volume of water intercepted, infiltrated, stored,
evaporated, or transpired and snbtracting it from the precipitation.
HEC-~h~v~S is designed to simulate the surface runoff response of a dra/nage basin to
precipitation input. The model represents the basin as an interconnected system of hydroio~c
and hydraulic components. Each component models an aspect of the precipitation-runoff
process w/thin a portion of the basin commonly referred to as a subbasin. A component may be
a smfface runoff entity, a stream ct~,annel, or a reservoir. The result of the modeling is the
computation ofs~eam flow hydrographs a~ desired locations in the drainage area.
NRCS methodology was used to determine runoff volnmes, d/rect r~moff and channel routing.
The advantage of the N-RCS 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
rou~-ag, and differing laud uses can only be accounted for via the runoff curve number. Ln the
Drainage Basin Mast~ Plan analysis, the N-RCS methodology was used.
Ci~i of D~lb~iq,ie. Jowa Drainage Be. sin ?/[asrer Pla~
METHODOLOGIES
Key data required by the FIEC-F2VIS model include:
· Drainage basin area~
· Precipitation dep~s;
· tlunoffanrve number;
· Unit hycl~o~nph and basin lag t/me;
· Design storm characte,dStiCS; and
· Channel and rese~-oir roming parameters.
2,3.:~ Model Schem~atic
HJ~C-F,~MS dynamically routes storm water through open charmels. Hydraulic muting tB~ou~
~ainage systems requires a mathematical ~amework ~kom which nume~ca] calculations can
take place. ~C-HMS uses a li~-node concept to idealize r~aI-wor]d systems. ~is concept
requires a n¢~'ork of nodes or junctions and ]i~s or reaches represan[ ~e drainage system. A
node is a discrete location in the drMnag¢ system where conse~ation of mass or continuity is
maint~ed. Li~s ~e ~e co~ecd0ns be~een nodes and are used to ~ansfer or convey water
~ough the drayage system. ~e following general guidelines were used to locate nodes in ~e
drMnage area schematic:
1. Upstream and downstream of any structure (e.g., culve~s, weirs, etc.); .
2. Ponds and lakes (specifically storage nodes);
3. Channel junctions;
4. ' Downstream boundary;
5. ' Where charmeI ge.ometry changes abruptly;
6. W~nere the channel bed slope changes abruptly; and
7. Where major surface inflows to the conveyance system.
By followLng the general guidelines, a schematic dia~am of the drainage area conveyance
system was developed. The drainage area drainage areas were delineated and subdivided us/ag
the DAGIS mapping. The two-£oot contom- inteD'al on the GIS mapping provided useful
information in determining Uhe major drainage area divides and subbasin delLneation. The
drainage area was segmented into subbasins based on selected design points.
City of Dubuque, iowa
Methodologies
Drainage -~a$in J/faszer Pla~
Fall 2001
]~IETHODOLOG]'E~
22.2 NRCS Runoff Curve Number
The Nararal Resources Conservation Servine (7'lACS) m.noff curve number procedure was used
lo compute abstractions for storm rainfall. Absn-actions are defined as the physical process (such
as soil infiltration smd detention or retention by vegetation), which effectively reduces the
volume of precipitation, wtfch becomes runoff. The rainfall in excess of the abstractions
becomes .ranoff and is relented to as excess rainfall. Excess rainfall is always tess than or eo~a]
to the depth of precipitation. The crowe number is a function of land use, soil t;ype, conditio~ of
cover, and antecedent moisture condition. This information was' used in conjunction with
information Eom the Dubuque County Soil Survey, GIS mapping and city's drainage
standards/cfite~a to develop a nmoff curve number for each subbasin. The soils ar,e generally
characterized as hydrologic soil ~oup 'B', which have moderate infikraion rates if thoroughly
we~ed, and consisting of deep or well drained soils with moderately fine to coarse textures. The
average ~ntecedent moisture condition (AMC-II) was assumed. The curve numbers are based on
the tables published by the N~R. CS in Technical Report 55 (TR-55). Table 2.2 summarizes t~he
land use ctassiiication and its respective curve number.
In subbasins where development is partially or fully developed, the hydrologic analysis was
pe~ormed for ukimae land use development. In subbasins where a~m-icult ~uraI development was
present, the hydrololdc analysis was performed as al~iculmral land use, because developers are
reqnked to provide on-site detention to maintain existing runof£ releases.
Table 2.2
Drainage Area Land Use Groups and Curve Number
ST
S~eets 99
tNrD ~dustr/a! 88
CO Cormmerciat 92
INS ! Institutional 88
ED High Density ResidendaI 85
M-D Medium Density Residential 75
LD Low Density Residential 72
AG A~msculmral 73
OP Open Space and Grass 69
Methodologies 2-5 Fall 2001
METHODOLOGTE5
2,3.3 NRCS Unit Hydrograph
The unit hydrograph method is Cne component in the rMnfalt-nmoff mode] that transfon.s the
~fall excess into a surface,mno~= hydro~aph. The unit h~&o~apn' ~ ' r~resents a t~icai
hydro~aph shape for a drainage ~¢a. The u~t hydro~aph for a ~nag¢ ~¢a is defined as a
d~¢ct mnoffhydro~aph resulting from one inch of excess rMnfM1 generated unifo~ly over the
dr~ag¢ ~¢a at a constant rate for a sto~ of a specified d~afion.
The is'RCS unit hydrograph method relates hydro~aph characteristics to a physical characteristic
of the drainage ar¢a, the basin time to peak, tw The basin time to peak is defined as the time from
thc beginning of the rainfall event to the time at wkich the peak runoff rate is observed at the
drainage area outlet. The time to peak can be estimated using the follosving empirical equation:
At
t~ = _~-+tl~~
where:
tp
tlag
time to peak, in hours
computational interval, in hours
~'~Tl.e, ~n hours
lag ';
The lag time is defined as the time difference between the center of mass of the rainfall excess
and thc peak of the upfit hydrograph. Lag times for each subbasin within the draLnage area were
computed by applying the cra'ye number method in the GIS analysis. The lag time is ~ve by the
following equations:
L °'s (S + 1)
1900 yo.~
1000
S= -t0
CN
where:
ti=g = lag nme, in hours
L = greatest flow length, in feet
Y = average drainage area slope, m percem
CN = runoff crowe 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,
Ct? of Dubuque. Iowa
J/f e'.hodologze$
Drainage -~aszn J/faster Plan
2-6 Fail 200t
METHODOLOGIES
2.3,4 Rainfall
The 24-hour raknfall depths for the t0-, 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 Elinois State -vVater SurYey publication, Bulletin 7t, "Rainfall Frequefcy Atlas of the
M/dwest". The po:ur data values are hi,er than the areal mean relations detei-mined for each
c!Lmatic section in the state o£Iowa. The hydrolo~c analyses were conducted using the h/gher,
more conservative point data values. Tl~e 500-year rainfall depth was extrapolated from the
t0-, 50- and 100-year values: A2-ea rainfall reduction factors were not used to.reduce the point
rainfali depth because the drainage areas were less than I 0 square miles.
Table 2.3
City of Dubuque 24-Hour Total Rainfall Depths
1 O-Year 4.5
50-Year 6.0
t 00-Year t 7.0
500-Year [ 11.0
In order to calibrate the hydrolo~c model, a comparison of the basin ruaoff to other hydrologic
methods was made. ,A~n observed hydrograph, depicting flow rates over time, was not available
for any storm events to calibrate; therefore, another method was sought. Hydrolo~c analysis has
been conducted for Catfish Creek and its tributaries in the 1989 Federal Emergency Management
Agency (FEM_A) Flood J2surance Study (FIS). The North Fork of Catfish Creek was the first
drainage basin to be studied; therefore, a comparison of the i00-year FIS resuhs and 100-year
HEC-FLMS results were evaluated. North Fork of Catfish Creek i} an ungaged stream, so
synthetic methods were used to obtain the discharge-frequency relationships in the FIS. In
addition, the Iowa Depaw. ment of Transportation's (IaDOT) regression equations were compared.
A summary of 100-year peak d/scharges is shown in Table 2.4.
ci~. of Dubuque, Iowa DraiNage Basin Master P&n
Mer3.odologiex 2-7 ~--rzlI 2001
M ETHODOLOGI'ES
Table 2.4
North Fork Catfish Creek Peak 100-Year Discharge Comparison
at Confluence with Middle Fork Catfish Creek
IaDOT [ 2,500-3, i 40 Developed for mrai Iowa ~fi~age basins.
FEMA-FIS 3,600 Flood Insurance Smd,',' using regression
equations. Based on existing land use
conditions.
HEC-HMS 2,950 ~ Existing land use conditions with no
I effective storage. T~vp. e-II dis~bufion.
HEC-HMS 3,200 Existing land use conditions ~th no
effective storage. Modified Type-II ramfalI
~ dis~bution.
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 b~ins and urban effects are not recognized. In
order to simulate the FIS discharges~ modifications to the ixfRCS Type-II ra/nfalI distribution
were made. The modification was performed to account for the'qMck runoff response of
Dubuque soils. The hyetograph for each basin was developed using a 15-minute time increment
and a modification of the RrRCS Type-H rainfall distribution by including the 6-hour rainfall '
hyeto~aph within the 24-hour hyeto~aph. 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. ~fis modification produced favorable discharges to the FIS discharges.
Ci.,y of Dubuque. Iowa
2?£e~.hodolog'ies
Drainage $~in _,!4as:er Plan
Fall 2001
METHODOLOGIE$
Table 2.5
City of Dubuque 15-Minute Time Distribution for 24-Hour Storm Event
0.000
0.007
0.010
o.olo
0.010
1.25 I 0.0i0
I.$ 0.010
1.75 0.010
2 0.010
2.25 i 0.010
0.010
0.0t0
0.010
0.010
0.010
0.010
0.0t4
0.0t4
0.014
0.0t4
0.0!4
0.014
0.014
0.0t4
0.014
0.0i7
0.017
0.017
7.2'5 0.017
7.5 0.0t7
7.75
0.0i7
0.014
0.014
0.014
0.014
0.014
)14
0.014
0.000 0.000
0.012
0.018
0.0i8
0.018
0.018
0.018
0.018
0.0t8
0.02I
0.032
0.0~_
0.032
0.032
0.0.>2
0.032
0.032
0.0t4 0.018 0.032
0.014 0.018 0.032
0.032
3.014 ] 0.018
3.0!4 t 0.018
D.O14 0.018
).014 0.018
0.014 t 0.018
).018 I 0.024
0.018 I 0.024
0.018 i 0.024
,0.018 ! 0.024
0.018 [ 0.024
0.0t8 t 0,024
0.024
0.024
0.024
0.030
0.030
0.030
0.030
0.018
0.018
0.0t8
0.023
0,023
0.023
0.023
0.023
0.023
0.030
0.030
0.030
0.032
0.032
0.032
0.032
0.042
0.042
0.042
0.042
0.042
0.042
0.042
0.042
0.042
0.053
0.053
0.053
0.053
0.053
0.053
0.053
8ig5: 0.021
).024
8;:75 ; 0.024
,: 0.024
9i25] 0,028
915:7 0.042
9.575 0.042
!0 0.046
0.056
0.023 0.030
t 0.027 i 0.036
0.032
0.032
j 0.032
0.036
0.056
0.056
0,061
O.042
0.042
0.042
0.058
0.063
0.063
0.068
0,053
0.064
0.074
0.074
0.074
0.085
0,085
0.096
0,096
0.075 0.084 0.1t2
0.056 0.075 0.084 0.127
0.070 0.094 0.105 0.159
0.070 0.094 0.t05 0.191
0.095 0.127 0.142
0.160 0. I79
0.259 0.289
0.223
0.276
1.104
2.930
1.495
0.066
0.056
0.053
0.042
0.042
i$~:.75;:] ]:;; 0.042
:1;5 ; 3.039
s.2S 0.024
I 0.021
1:5.5
15. 5 ':! o.o21
2.007 2.242
0.53t 0.593 0.791
0.230 0.257 0.343
0.146 0.163 0.244
0.t18 0. I31
0.103
0.1t6
0. I91
0.159
0.!00 0.138
0.084 0.117
0.079 0.106
0.063
0.063
0.063
0.058
0.042
0.036
0.089
0.075
0.071
0.056
0.056
0.056
o.052
0.0-,_
0.027
0.027
0,0.~6
0.096
0.085
0.084
0.077
0.074
0.064
0:064
Cisg of Dubuque, Jowa Drainage Baxin Master ~ian
Mezhodotogies 2-9 Fall 2007
METHODOLOGIES
Table 2.5
City of Dubuque 15-Minute Time Distribution for 24-l:iour Storm Event
~ ] ,' . .~. Ret~ra,Pemod . , ~,,.: . : :-~.t~ ',,'i~'~7~/:~,Re:rurn Period: ,,
t6.25. ~ 0.021 0.027 0.036 0.064 . ~:~0::7:'.'['.. 0.0~0 ~ 0.014 ~ 0.018 0.032
iS.5:~.I 0.021 0.027 0.036 0.064 ~::20:75 '.:0.0~0 ~ 0.0~4 ~ 0.0~8 ~ 0.032
~7.s" ~ o.o~7 ~o.o:2I o.o~o [ o.oss ~ :~.*s I o.o~o ~ o.o~4 ~ o.o~s ~ o.o~:
~8.:s ~ o.o~4 o.o~so.o2~ ~ o.o42 o~:.s I o.o~o ~ o.o~4 I o.o~s ~
~.ls:Ts:: :~ 0.0~4 o.o~s0.0~4 I 0.042 0.0~0 i 0.0~4 I o.o~s ~ 0.0~:
:: 53' 5' ~
.~¢.:s~.?~.: o.o~4 o.o~so.o~4 Io.o42[ ~o.o~o ~ o.o~ [o.o~so.o~2
:~19.5-~ 0.0~4 0.018 0.024 ~ 0.042 [":~:.7~:'::'[.~ 0.0~0 ~ 0.0~4 ~ 0.0~8 0.03~
· ::~927s :' 0.0~4 o.o~s 0.02~ 10.04: ~-::~2i:':.~:~:::..I 0.007 ~0.009 lo.on
~0::::::::~:': 0.0~0 0.0~4 o.o~s I 0.0~2 [iOt~::::~:.~ 4.s I 6.0 ~7.0
2.3.5 Channel Routing
Routing pf flood flows from the outlet of an upstream subbas/n to the next subbasin outlet was
accomplished using the Muskingum routing method in HEC-~MS. Data /nput for the
Muskingum consists of a storage correlation coefScient and a travel time for a reach. The storage
correlation coefScient ig a measure of how closely storage in the reach is related re outflow.
Based on sensitivity analyses performed duping the project it was shown to be a relatively
insensitive variable. A value of 0.2 was used t2nroughout the study area. The travel time throu~__2u
a g/yen reach was calculated using G!S mud based on an assumed veloci~ of 3.3 feet per second
(1 meter per second).
2,3,6 Reservoir Routing
Reservoir routing was incinded [n ~e model to account for ~e flood attenuation effects
associated with roadway storage and existing and potential detenfio~ basins. The HEC-~DviS
Modified Puls routing routines were used re simulate 5ow through fine reservoirs using the level
Ci~ of Dubuque, iowa
k/ethodologies
£aff 200]
]VIETHODOLOG!ES
pool routing proced'are. This procedure assumes the reservoir water surfase remains effectively
level dufing 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
rdafionsbJp for the upstream reservoir pool. The stage-storage relationship was derived from
GiS mapping. Stage-discharge rating tables were developed using infonnation on the outlet
works facilities obtained in the field. Assuming iriet control, a stage-discharge relationship was
generated using homographs contained iL the Federal Highway Administration's (FHWA)
Hydrantic Design Series No. 4 (t-EDS-4).
2,3.7 CRWR-PrePro
A preprocessor was developed by the Center for Research and Water Resources (CRWR) at the
UniversiW of Texas, Austin, under the superw~sion of Dr. David Maidment. CRg/iK-PrePro was
used to develop the inpnt data for the hydrolo~c model.
CRWR-PrePro is a GtS preprocessor for the Hydrologic Engineering Center's (HEC)
Hydrolo~c Modeling System (HEC-HMS). HEC-HMS is currently being developed by HEC as
pm--t of the NexGen program of research. The purpose of CRWi~-PrePro is to summarize data
from a GIS system for hnput to HEC-t-EMS. Ct~W~-prePro uses stream and subbasin GIS layers
as input data. S~eam and subbasin data layers are reqnired as input, and the sofwcare requires
the use of metric mn/ts. 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.ay).
The data sets must be in the same geographic coordinate system, and the input data must
accurately describe the hydrolo~c properties of the area. Errors occur due to discrepmncies
mmong the stremm and subbasin data layers.
The program code is oriented around identifying hydrolo~c elements and the relationship
ber~veen these elements. Seven (7) hydroto~c elements are identified: subbasins; sources;
reaches; junctions; res~mw'oirs; diversions and sinks.
The step-by-szep methodology for developing a HEC-HiMS basin file using CRW-R-PrePro is
presented beto~v. These steps produce a HEEC-~kMS basin fi!e, which is then imposed into tJ~C~
PLMS.
City of Dubuque, lowa Drainage &~in Plaster Plan
!kfe~hodoiogfes 2-77 Fall 200.7
METHODOLOGIES
Table 2.6
Spatial Data for CRVv~R-PrePro
DEM D~=l;al elevanon model (DEM), 10 meter ~d o, elevat~ons desert rang
topo~aphy, developed ~vm the Distal T~in Model (D~i) w~hkin
DAGIS dataset.
~' Shape file of s~eams or reaches developed by hhe EPA, au~ented by
DAGIS data.
LU Land use shape file developed from DAGIS data.
STATSGO State Soil Geo~aphic database, soil ciassificarions, developed by U.S.
Geolo~c Su~'ey
Ae~al Photos Ae~aI photo~aphy used for identifying s~cmres and other ~bamres.
1. Develop a GtS 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. Lntersect the stream shape file with the DEM to assure the streams delineated from
the DEM match those from the EPA reach file (1L0.
3. Fill the DEM sinks so sumps do not cause incorrect flow directions.
4. Compute the flow direction for each grid point withha the DEM.
5. Compute a flow' accumulation grid based on the number of cells draining to each
point.
6. Consn-uct a stream network based on a user de£med accumulation threshold.
7. Streams may be added to the stream network if they were not included in step 6.
$. Segment streams into reaches.
9. Place outlets at the junctions of each stream reach.
t0. Add additional outlets where necessary (i.e. at structures).
11. Delineated drainage areas from each of the outlets ushng the DEM.
12. Streams and drainage area ~hds are convened to vector shapefiles.
13. Subbasins maybe merged.
14. Calculate runoff curve numbers based on la~d use and soil classification.
15. Determine lag thm~ based on basin topo~aphy.
16. Determine Mustdngum coefficients based on chavmel characteristics.
Ci~- of Dubuque, iowa
~ethodologfes
Drainage 2~asin 2Picketer ?lan
Fall 200)
METHODOLOGiES
17. Export the data set to a ~C-Hlk[~S basLn file.
1 $. L~npo~ The H]6C-~MS basin file into a HEC-I~'ViS project
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 hncluding water surface elevations mud hydraulic capacities
of existing drainage structures. Peak runoff rates computed as part of the hydrologic modeling
were used in conjunction w/th the GIS and limited field data to develop open channel and closed
conduit hydraulic models. For the open channel model, water snrTace pro5les were com_futed for
the 10-, 50-, I00- and 500-ygar return pe~od flood events. The resulting 100-year floodplain for
ultimate development with and without project conditions was delineated uskng GIS. A portion
of the North Fork Catfish Creek main cha'meI was modeled with a hydraulic model. The closed
conduit model xvas used to analyze the hydraulics of the Bee Branch main storm sewer tnmk
tine. The 10-, 50-, and 100-yea- return pmdod flood events were investigated. The following
sections descr/be ~e key elements involved in the hydraulic modeling of the stream segments in
the City of Dubuque.
The Hydroto~c En~neering Center - River Analysis System (HEC-RAS) was used to analyze
open chamnet hydraulics. HEC-RAS is a hydraulic model developed by the U.S. A-ray Corps
Engineers. The model is desig-ned to perform one-dimensional hydraulic calcutafinns for a
network of natural and constructed open chapmels: The followLng assmuaptions are used by' HEC-
RAS in computing water surface profiles:
· Steady flow;
· Gradually vari6d flow;
· One-dimensional flow;
· Channel slopes are small, less than 1:10
A2thou~n some of the steeper cha~.els may exhibit supercritical flow characteristics, it is
consercative to base the hydraulic analyses on subcrifical flow, since the depth of flow for
subcritical flow- conditions is greater than supercrkical flow conditions.
X~P-S-CFb/LM was used to analyze closed conduit hydraulics. XP-S-W2v~M is proprietary storm
w-a*.er modeling software based on the U.S. EnvirommentaI Protection Agency model S'¢/2X4M
(Storm Water Management Model). ~-SWMM is capable of modeling unsteady ~low allowing
for mna/ysis of changes in flow vmdables wkh time and attenuation of peak disch~ges as a result
CIE,, of Dubuq~te, 7owa Drainage Basin ~Iaxzer ~[an
Methoda~.ag'ies 2-73 ~aH 200/
MFTHODOLOGI~S
of storage. The following ass'oznprions are used in hydranHc computations performed by XP-'
SW~L~:
Gradually varied flow;
· One-dimensional flow; and
· SubcriticaI flow
2.4,1 Model Schematic
For the open channel model, channel eross-Jecfion geomet~ and flow lengths were obtained
from a triangular irregular model (T~ developed ~om ~e distal te~ain model ~TM). Cross-
section geometry was generated ~om the T~ and the U.S..~y Co~s of En~neer's HEC-
Geo~S softw~e in conjunction with .~cVi~w's 3D-~Myst which electronically generates the
HEC-~S inpm files within McView. Bridge and culvem geomet~ were obtained ~om field
me~urem~ts. Ma~ng's rou~ess coefficients w~re selected based on field observations and
intepretations ~om aefiM mapping. GuidelNes contained in "Open Ch~el Hydraulics," by
Chow, were used when est~ating rou~ess coefficients.
The closed conduit XP-SWMM model was generated based pF~marily on information supplied
by the City. The DAGIS storm sewer coverage provided the storm sewer ali=mnrnent in the area
of interest, and model geometry was based on storm sewer profile sheets with additional
information obtained from the City's archive. Marming's rougbmess coefficients were selected
based on conduit material information taken ~om stonm sewer profile sheets and
i-ecommendafions made by City en~neefing stuff. Guidelines contained in "Open Channel
Hydraulics," by Chow, were used when estimating rougJxneas coefficients.
2.4.2 < Model Calibration
Several h/gh-water marks were evaluated for the May 16, 1999 storm event. This 1999 storm
was estimated to be a 75-year return period. High-water marks were used for an order of
magnitude assessment of the model results. No additional calibration of the hydraulic model w-as
performed.
2.4.3 Channel and Structure Improvements
Channel knprovements were evaluated for a number of problem areas identified in the study.
I-t_EC-I~S offers a convenient method for analyzing a range of charmel improvement options
and includes computational proced'~es for estimating excavation volumes and compu~Sng
City of Dubuque, Iowa
~/e&odologies 2-f4
Draiaage 3axia Master
Fail200]
APPENDIX B
INSURANCE SCHEDULE C
INSURANCE REQUIREMENTS FOR PROFESSIONAL SERVICES
All policies of insurance required hereunder shall be with an insurer authorized to
do business in Iowa. All insurers shall have a rating of A or better in the current
A.M. Best Rating Guide.
Ail policies of insurance required hereunder shall be endorsed to provide a thi¢.y
(30) day advanced notice to the City of Dubuque of any cancellation of the policy
prior to its expiration date. This endorsement supersedes the standard
cancellation statement on the Certificate of Insurance.
shall furnish Certificates of Insurance
to the City of Dubuque, iowa for the coverage required in Paragraph 7. Such
certificates shall include copies of the endorsements set forth in Paragraphs
2 and 5 to evidence inclusion in the policy, shall
also be required to provide Certificates of Insurance of ail subcontractors,
and all sub-subcontractors who perform work or services pursuant to the
provisions of this contract. Said certificates shall meet the same insurance
requirements as are required of
Each Certificate of Insurance shati be submitted to the contracting
department of the City of Dubuque, Iowa prior to commencement of
work/service. (The contracting department shall submit the ce~ificates to the
Finance Director.)
Alt policies of insurance required in Paragraph 7, except Professional Liability,
shall include the City of Dubuque, iowa under the attached Additional Insured
Endorsement (CG2026) and the attached Governmental Immunities
Endorsement.
Failure to provide evidence of minimum coverage shall net be deemed a
waiver of these requirements by the City of Dubuque. Failure to obtain or
maintain the insurance required herein shall be considered a material breach
of this agreement.
, subcontractors, and ail sub-subcontractors
shall be required to carw the following minimum insurance coverages or
greater if required by law or other tegal agraembnt:
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PROFESSIONAL LIABILITY: $ i ,000,000
COMMERCIAL GENERAL LIABILITY:
General Aggregate Limit
Products-Completed Operation Aggregate Limit
Personal and Advertising Injury Limit
Each Occurrence Limit
Fire Damage Limit (any one occurrence)
Medical Payments
82,000,000
$1,000,000
$1,000,000
$1,000,000
$ 50,000
$ 5,000
Commercial general liability shall be written on an occurrence form, not a claims
made form. Coverage to include premises-operations-products-completed
operations, independent contractors coverage, contractual liability, broad form
property damage, and personal injury.
UMBRELLA OR EXCESS LIABILITY:
$2,000,000
Revised January, 2002
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POLICY NUMBER COMMERCIAL GENERAL LIABiLiTY
TH!S ENDORSEMENT CHANGES THE POLICY. PLEASE READ IT CAREFULLY.
ADDITIONAL INSURED - DESIGNATED PERSON OR
ORGANIZATION
This e~dorsemen~ modifies insurance provided under the fallowing:
COMMERCIAL GENERAL LIABILITY COVERAGE PART.
SCHEDULE
Name of Person Or Organization:
The City of Dubuque, including ali its elected and appointed officials, ail its employees and volunteers ali
its boards, commissions and/or authorities and their board members, employees, and volunteers. -'
(If no entry appears above, information required to complete this endorsement will be shown in the
Declarations as applicable to this endorsement)
W'HO tS AN INSURED (Section II) is amended to include as an insured the person or organization shown
in the Schedule as an insured but only with respect to liabili~ arising out of your operations or premises
owned by or rented to you.
Coovdaht. insurance Servi~s Of%e. inc. 1994
CG 20 26 11 85
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CITY, OF DUBUQUE, IOWA
GOVERNMENTAL IMMUNITIES ENDORSEMENT
Nonwaiver of Governmental Immunity The insurance carrier expressly agrees and
states that the purchase of this policy and the including of the City of Dubuque, Iowa
as an Additional Insured does not waive any of the defenses of governmental
immunity available to the City of Dubuque, Iowa under Code of Iowa Section 670:4
as it is now exists and as it may be amended form time to time.
Claims CowragLe_ The insurance carrier further agrees that this policy of insurance
shall cover only those claims not subiect to the defense of governmental immunity
under the Code of lowa Section 670.4 as it now exists and as it may be amended
from time to time. Those claims not subject to Code of Iowa Section 670.4 shall be
covered by the terms and conditions of this insurance policy.
Assertion of Government Immunity The City of Dubuque, Iowa shall be responsible
for asserting any defense of governmental immunity, and may do so at any time and
shatI do so upon the timely written request of the insurance carrier.
Non-Denial of Coverage. The insurance carrier sha!l not deny coverage under this
policy and the insurance carrier shall not deny any of the rights and bgnefits
accruing to the City of Dubuque, Iowa under this policy for reasons of governmental
immunity unless and until a court of competent jurisdiction has ruled in. favor of the
defense(s) of governmental immunity asserted by the City of Dubuque, Iowa.
J:9_o Other Change in Policy. The above presen¢ation of governmental immunities sha!]
not othen~vise change or alter the coverage avaiIable under the policy.
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