Bee Branch Creek Align. StudyMEMORANDUM
TO:The Honorable Mayor and City Council Members
FROM:Michael C. Van Milligen, City Manager
SUBJECT:Bee Branch Creek Alignment Study RFP
March 7, 2003
Due to concerns raised, the Bee Branch Creek Restoration Project was divided into two
phases. The portion of the creek from 16th to Garfield has been adopted at part of the
Drainage Basin Master Plan (DBMP). The second phase of the project, estimated at
$10.2 million, and running from Garfield to 24th and Elm Streets was not adopted as part
of the DBMP and remains under consideration. On December 16, 2002, City Council
authorized staff to issue a request for proposals (RFP) to do preliminary design and to
conduct an alignment study for the Bee Branch Creek Restoration Project. Before the
City Council can give further consideration to the Bee Branch Creek Restoration Project
from Garfield to 24 and Elm Streets, there are a number of issues related to design
and alignment that need to be addressed. The objective of the Bee Branch Creek
Alignment Study is to address those issues.
Attached is a proposed RFP for the Bee Branch Creek Alignment Study. The purpose
of this study will be to:
1. Establish the optimum alignment for the open waterway based upon existing
constraints;
2. Provide a preliminary design that establishes what the waterway will look like and
how it will function before, dudng and after rainstorms of different magnitudes;
and
3. Work with a citizens advisory committee made up of representatives from
impacted neighborhoods in developing the alignment location and design.
I concur with the recommendation and respectfully request Mayor and City Council
approval.
Michael C. Van Milligen
MCVM/cs
Attachment
cc: Barry Lindahl, Corporation Counsel
Cindy Steinhauser, Assistant City Manager
Mike Koch, Public Works Director
Gus Psihoyos, Assistant City Engineer
Demn Muehdng, Civil Engineer
CITY OF DUBUQUE, IOWA
MEMORANDUM
March 6, 2003
TO:Michael C. Van Milligen, City Manager
FROM:Gus Psihoyos, Assistant City Engineer
SUBJECT:Bee Branch Creek Alignment Study Request for Proposals (RFP)
INTRODUCTION
The proposal review committee has drafted an RFP for the Bee Branch Creek
Alignment Study. The committee seeks the City Council's endorsement of the RFP.
BACKGROUND
Due to the concerns raised, the Bee Branch Creek restoration project has been divided
into two projects (or two phases). The portion of the creek from 16th to Garfield (Phase
I), estimated at $6.9 million, has been adopted as part of the Drainage Basin Master
Plan. Phase I, which will take up to three years to construct, is included in the FY 2004
- 2008 (5-year) Capital Improvement Project budget with initial funding available in FY
2006. The second portion (or phase) of the project, estimated at $10.2 million, from
Garfield to 24th and Elm has not been adopted as part of the DBMP. However, it
remains under consideration.
On December 16, 2002 the City Council authorized City staff to issue a request for
proposals to do preliminary design and to conduct an alignment study for the Bee
Branch Creek Restoration Project from 16th and Sycamore to 24th and Elm.
Before the City moves forward with the Bee Branch Creek Restoration Project from
Garfield to 24th and Elm, several questions and concerns related to the project must be
addressed. The objective of the Bee Branch Creek Alignment Study is to address those
concerns.
DISCUSSION
The proposal review committee; made up of Dr. Charles Winterwood, Long Range
Planning Advisory Commission Member; Cindy Steinhauser, Assistant City Manager;
Ken TeKippe, Finance Director; Gus Psihoyos, Assistant City Engineer; Jerelyn
O'Connor, Neighborhood Development Specialist; David Ness, Civil Engineer, Deron
Muehring, Civil Engineer; and Jerry Anderson, North End Neighborhood Association
representative have drafted an RFP for the study. As of this point the Washington Street
Neighborhood Council has not appointed a representative.
The selection committee's objective is to review proposals from consultants and
recommend to the City Council the engineering firm whom the committee feels would be
the best firm to perform the Bee Branch Creek Alignment Study.
The Bee Branch Creek Restoration Alignment Study will:
1)Establish the optimum alignment for the proposed open waterway along
its approximately 4,500-foot length based on existing environmental,
utility, social, and economic constraints;
2)Provide a preliminary design to a level that it establishes:
a. What the waterway will look like along its entire length and
b. How the waterway will function before, during, and after rainstorms of
different magnitudes; and
3)Work with impacted residents in the form of a citizens advisory committee
to ensure that the recommended alignment location and waterway design
are based on input from the neighborhoods impacted by the proposed
open waterway.
Although the design of an open waterway through a highly developed, densiy populated
urban setting is a challenge for even the most experienced engineering firm, a
significant prerequisite of the consulting firm will be its ability to work with impacted
residents. The Consultant must establish means 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; public meetings with neighborhood
groups; and presentations to the City Council.
The Citizen Advisory Committee (CAC) 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 an alignment and preliminary design that
considers the social and economic concerns and needs of the impacted residents and
neighborhoods. Stated another way, the CAC will be relied upon to establish the criteria
to be used when evaluating alternative alignments, prompting the selection of an
alignment to be recommended to the City Council.
The schedule for the selection of a consulting firm is as follows:
RFP sent to firms: March 18th
Responses due: April 15th
Committee to establish Short List: April 22nd
Interviews Conducted: April 28th through May 2nd
Committee to Select Firm: Week of May 5th
Committee to Recommend Firm to City Council: May 19th
With these dates as a guide it is anticipated that the consultant would initiate the project
in June. The project will require between nine and eighteen months to complete.
RECOMMENDATION
I recommend that the City Council approve the RFP for the Bee Branch Creek
Alignment Study.
BUDGET IMPACT
The engineering cost for the Bee Branch Alignment Study is estimated to be between
$250,000 - $400,000 depending on the scope of services selected. The project will be
funded from a Fiscal Year 2003 General Fund Appropriation in the amount of $250,000.
If required, prioritization of the Fiscal Year 2004 CIP budget can provide additional
funds for the study.
ACTION REQUESTED
I respectfully request that the City Council approve the RFP for the Bee Branch Creek
Alignment Study.
CC:Cindy Steinhauser, Assistant City Manager
Pauline Joyce, Administrative Services Manager
Ken TeKippe, Finance Director
Michael A. Koch, Public Works Director
Jerelyn O'Connor, Neighborhood Development Specialist
Deron Muehring, Civil Engineer
David Ness, Civil Engineer
Dr. Charles Winterwood, Long Range Planning Advisory Commission Member
Jerry Anderson, North End Neighborhood Association Representative
Dan Shireman, Washington Neighborhood Council President
attachment
REQUEST FOR PROPOSALS
CONSULTING ENGINEERING SERVICES FOR THE COMPLETION OF AN
ALIGNMENT STUDY FOR THE BEE BRAN 3H CREEK RESTORATION PROJECT
FOR THE CITY OF DUBUQUE (IA)
The City of Dubuque ("City") is seeking the services of a qualified engineering firm for
the Bee Branch Creek to establish the alignment for the Bee Branch .Creek Restoration
Alignment Study.
I. INTRODUCTION
Dubuque is located in northeastern Iowa .ust across the Mississippi River from
Illinois and Wisconsin The City is approximately 30 square miles in area, with a
population of nearly 60,000 persons. Providing a full range of services, the City's
annual operating and capital budget is nearly $100 million More information
about the City organization can be found on the City's official web site at
www.cityofd ubuque.org.
Dubuque's terrain is widely varied, with steep hills, bluffs, and a flat area
protected from the Mississippi River by a floodwall. 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. 32na Street to the
north, Asbury Road and University Ave. to the south, NW Arterial to the west,
and the Mississippi River to the east (see Figure 1). 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 flats where it is collected in the "Bee
Branch" storm sewer.
The Bee Branch storm sewer originates approximately 625-feet west of the W.
32nd 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 at the W.32nd Street detention
basin to a 20-foot by 12-foot stone box where it outlets into the 16th Street
detention cell. Stormwater flows from the 16th Street detention cell into the
Mississippi through the floodwall during normal river stages and is pumped
during high river stages.
The Bee Branch storm sewer was once a creek that meandered through the
north end of Dubuque. Over a period of decades the creek was straightened,
03110/2003
lined with limestone, and eventually covered - transformed into the Bee Branch
storm sewer that exists today.
Figure 1. Bee Branch drainage basin limits within the Dubuque city limits.
Background
As HDR Engineering (Omaha, NE) was preparing a Drainage Basin Master Plan
(DBMP) for the Bee Branch watershed, the drainage problems in the Bee Branch
watershed basin became evident to all in the late hours of May 16. 1999. A
severe thunderstorm moved over Dubuque producing between two and a half
(2.5) and five (5) inches of rainfall in a six hour period, the later indicating
between a 50 and 75-year rainfall event. The resulting damage to infrastructure
03/10/2003
2
and private property prompted a Presidential Disaster declaration for Dubuque
County.
In July of 2001, HDR presented the preliminary DBMP to the City Council The
plan reports that there are over 1 150 homes and businesses in the Bee Branch
watershed basi~ at risk of flood damage during a 100-year rainfall event. Four
projects (see Table 1) are outlined in the plan to reduce or eliminate this risk.
Table 1. Bee Branch Watershed Basin Improvements Recommended by HDR gineedng.
Approximate Homes &
Required Businesses
Improvement Description Number of Remaining
Homes & Est. Cost In the
Businesses Floodplain
To Construct
None Existing Conditions 1, I70
Upper Carter Build an earthen berm to
Detention Basin create 182 acre-feet of $875,000 Not
storage. Established
Purchase 15 homes
surrounding the existing
W.32~ Street basin and excavate 15 970¢}
Detention Basin within the basin to $4,023,000
increase the available
storage 100% to 94
acre-feet.
Grandview & Build an earthen berm to
Not
Kaufmann create 44 acre-feet of $530,000
Detention Basin storage. Established
Open 150' wide flood-way from
Waterway the existing 16t~ Street 17 645(2)
from t6t~ St. to detention ceil to Garfield $6,900,000
Garfield Ave. and Pine Street.
Open 150' wide flood-way from
Waterway Garfield Ave. and Pine 53
from Garfield Street to 24t" and Elm $10,200,000 < 5(3)
to 24~ Street. Streets
TOTAL 85 $22,528,000
After the construction of the Carter Roac detention cell cna modifications to the
existing W32nd Street detention ceil.
After the construction of the Carter Road detention cell. modifications to the existing
W32nd Street detention cell. and construction of the channel from 16TM St. to
Garfield.
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 24®
and Elm.
03/10/2003
The "Open Waterway" identified in Table 1 stretching from 16th Street to
Garfield and then from Garfield to 24th Street is what is now referred to as the
Bee Branch Creek Restoration Project. The proposed 4.500 foot long channel
was conceptually described as an open waterway with a 76-foot bottom width
and mildly sloping landscaped-banks to a depth of approximately ten feet.
requiring a 150-foot wide corridor.
In October 2001, City staff presented the DBMP to the NoAh 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. Citizens voiced their concerns related to relocating families and the
impact the channel would have on the neighborhood. Depending on the
alignment, building the channel from 16th Street to 24th and Elm would require the
purchasing of approximately 70 homes/businesses.
In February 2002, 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."
In the months that followed, a growing number of citizens impacted by the
flooding voiced their desire for the City to move forward with the improvements
recommended in the DBMP. A petition was submitted to the City Council that
indicated that hundreds of citizens support the proposed open waterway.
Due to the concerns raised, the Bee Branch Creek restoration project has been
divided into two projects or Two phases. The proposed open waterway concept
from 16th to Garfield. estimated at $6.9 million has been adopted as part of the
Drainage Basin Master Plan and the City is in the process of establishing the
funding to build the open waterway. The second portion (or phase) of the
project, estimated at $10.2 million, from Garfield to 24th and Elm is currently
under consideration.
Before the City moves forward with the Bee Branch Creek Restoration Project
from Garfield to 24th and Elm. several questions and concerns related to the
project must be addressed by the Bee Branch Creek Alignment Study.
PROJECT OBJECTIVE
The Bee Branch Creek Restoration Alignment Study will:
1)Establish the optimum alignment for the proposed open waterway along
its approximately 4,500-foot tength from the 16 th Street detention basin to
24th and Elm based on existing environmental, utitity, social and economic
constraints;
03/10/2003
4
2).Provide a preliminary design to a level that it establishes:
a. What the waterway will look like along its entire length - this includes
cross-sections at key points along the waterways length, as well as,
plan and profile sheets that indicated potential utility conflicts;
b. How the waterway will function before (normal conditions), during, and
after rainstorms of different magnitudes; and
c. The benefits and impacts of the proposed waterway.
3)Work with impacted residents in the form of a citizens advisory committee
to ensure that the recommended alignment location and waterway design
are based on input from the neighborhoods impacted by the proposed
open waterway.
III.SERVICES BY THE CITY
Information pertaining to the Bee Branch watershed-compiled by HDR
Engineerin9 (Omaha, NE) wi] 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 upon
request.
The City of Dubuque has a geographical information system referred to as the
Dubuque Area Geographical Information System or DAGIS. Available
topographical mapping includes 2-foot contours, digital terrain data. parcels.
building outlines, edge of pavement, storm sewers, sanitary sewers, water main.
and aedal orthogonal photos. The City's DAGIS is sufficient to determine partial
and total property takings associated with each proposed alignment.
The City will assist with the formation of the Bee Branch Citizen Advisory
Committee. in addition, the City will assist with BBCAC meetings by distributing
materials produced by the consultant to the BBCAC. securing the location
(facility) for each meeting; and, if conditions warrant, the City will provide the food
and refreshments.
IV.INFORMATION TO BE INCLUDED IN PROPOSAL
The proposal will include the following information and must 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 present material that illustrates the firm's experience and
expertise with this type of project.
03/10/2003
5
A. Provide the Firm's official name, address, and principal offices
B. Provide project references illustrating the firm's experience with:
1)Drainage improvement alignment studies;
2)Open waterway design in an urban setting;
3)Creek day-lighting projects:
4)Creek restoration projects:
5)Hydrologic and hydraulic modeling; and
6)Working with mpacted residents in the form of a citizen advisory
committee - building consensus.
For at least three references list:
1)Project name and location:
2)Contact person and telephone number;
3)Cost of work (actual cost vs. initial estimated cost);
4)Time required to complete the project: and
5)The role and responsibility of each member of the firm's
proposed "Bee Branch Creek Alignment Study" team on [he
referenced projects.
Provide abbreviated resumes highlighting their experience in relation
to the work referenced in part B above of the personnel who will be
working on the project (including sub-consultants). Include their
education, as well as. specialized and technical competence performing
the tasks they would be called on to do in conjunction with the Bee Branch
Creek Alignment Study.
Specify the Firm's ability to integrate this project into their work schedule.
The City expects the Consultant to identify specific tasks necessary to
meet the Bee Branch Creek Alignment Study objectives. Include any
thoughts that would improve the development of the plan and recommend
any work not identified in this RFP that is considered essential by the firm.
Include a pro!ect schedule outlining the time 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 utilized by the consultant during the project contract
period.
A preliminary scope of work and services
6
03/'10/2003
Responders should include in their proposal all tasks whether listed
herein or not, required to achieve the project goal. The following is a list of
some of the tasks to be included in the project scope.
1)Public involvement and project management
The Consultant must establish channels of communication that
promote input from impacted property owners. The following shall
be included: the formation of the Bee Branch Citizen Advisory
Committee; the completion of a survey (questionnaire), public
meetings with neighborhood groups; and presentations to the City
Council.
The BBCAC 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 an alignment
and preliminary design that considers the social and economic
concerns and needs of the impacted residents and neighborhoods.
The BBCAC will establish the criteria to be used to determine the
optimum alignment. The consultant must prepare more than one
alignment for consideration. Several design alternatives must be
considered for the recommended alignment (i.e. rectangular
stamped concrete channel with screening, multi-tiered grass lined
channel with plantings, use of the existing Bee Branch storm sewer
in conjunction with the open waterway, etc.).
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 set the agenda and prepare information for all
required meetings and public hearings. The necessary information
may include but is not limited to: invitation letters; hearing
handouts; and exhibits including maps, drawings, photos, and
slides.
2) The number of BBCAC meetings should depend on the
consultant's ability to react to direction from the committee.
Verify/establish existing drainage conditions
It will be the responsibility of the consultant to verify - to the
consultant's satisfaction - whether the computer models assembled
by HDR Engineering are appropriate to establish the design
discharge and the basin's hydrologic response. Compensation for
the consultant's time to make this determination shall be included
(whether specifically identified or not) in the cost proposal
submitted in response to this RFP. If the consultant determines that
the existing models are insufficient, the cost to create alternative
models must be included in the cost proposal submitted in
response to this RFP.
3)Design flows
The open waterway must be designed to convey the 100-year
recurrence interva rainstorm. In addition to consideration of the
100-year event, base flow and events of lesser magnitudes must
also be considered [o establish how the waterway will function
under a variety of conditions.
4)Determine channel characteristics
The design of the channel must include a description of the
materials (armor and vegetation) that would make up the thalweg,
scarp, and associated floodplain While the design shoutd be
considered preliminary, 91an and profile sheets must be included,
indicating potential conflicts with existing utilities. In addition.
multiple cross-sections are required along the 4 500-foot length to
fully illustrate the design characteristics to the BBCAC and City
staff.
5)Determine channel and floodway size
Based on the design criteria established by the BBCAC, the
consultant must establish the corridor size required to convey the
100-year runoff event.
6)Determine optimum channel alignment
7)Calculate the channel and floodway construction cost
Based on 1 through 6 above, calculate an updated cost to construct
the Bee Branch Creek Restoration Project.
Other jurisdictional permit requirements
The consultant should outline the environmental and jurisdictional
permitting issues and the potential roadblocks associated with day-
lighting the Bee Branch Creek.
1. The proposal should include a list of deliverables.
VII.EVALUATION CRITERIA
Proposals will be screened to ensure that they meet the minimum rec uirements
of the proposal format. A review of qualifying proposals will identify firms that
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):
03/10/2003
Qualifications and experience of the firm-reference checks, achievements
and completion of similar projects.
Project team-qualifications and experience with similar projects 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.
Grasp of the project requirements-the firm's understanding of the scope,
8
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-general attitude and ability to communicate to audiences
with varying technical backgrounds.
F. Qualifications/experience of the firm working with large groups of private
citizens, gresenting material, 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 based on the preliminary scope of
services.
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, which will include time for a question & answer period with
committee members. Each firm wilt be ranked based on the interview and overall
responsiveness to the RFP. The project schedule is as follows:
RFPs released to public: March 18
Responses due: April 15
Short list established: April 24
Interviews: April 28th through May 2nd
Consultant selection: Week of May 5TM
Committee to Recommend Firm to City Council: May 19th
The City of Dubuque is an Equal Employment Opportunity Employer.
VIII. FEES AND COMPENSATION
Separate the Fees and Compensation proposal (separate enclosure) from the
other pot[ion of the RFP submittal. While a contract wilt be negotiated after the
selection process has been completed, the cost proposal should include a
breakdown of costs - including the hours by individual tasks for the preliminary
scope of services.
Taxes
The City of Dubuque is exempt from all State sales tax. Do not inctude sales tax
in the Firm's proposal pnce. 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.
03/10/2003
9
IX. 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 April 15, 2003. The
address is:
City of Dubuque (Engineering)
C/O Gus Psihoyos. Assistant City Engineer
50 West 13th Street
Dubuque, Iowa 52001-4864
Each firm assumes full responsibility for delivery and deposit of the con"pleted
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 by any firm before the
execution of an agreement or contract. Nor shall the City of Dubuque be liable
for any costs incurred by the firms not specified in contract documents. The City
shall become owners of the proposals upon submission.
Appendix B outlines the insurance requirements for professional services,
Questions and correspondence regarding this RFP can be directed to Gus
Psihoyos (phone: 563-589-4275 or e-maih gpsihoyo@cityofdubuque.org) or
Deron Muehring (phone: 563-589-4276 or e-mail: dmuehrin@cityofdubuque.org)
from the City of Dubuque Engineering Division or by fax at (563) 589 - 4205.
03/10/2003
10
APPENDIX A
METHODOLOGIES
2.0 METHODOLOGIES
Flood hydrology models were developed for each individual drainage basin, incorporating the
un/que characteristics of each bas/n to simulate runoff for specific storm events. Stream
hydraulic models were developed for the segments included in tltis 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
th/s study.
2.1 PHYSICAL CHARACTERISTICS
2.1.1 Topography
Topography ora drainage area refers to the characteristics and features of the land surface, such
as slope and charmet width. The slope of a drainage area influences the rare at which
precipitation failing on the land surface will be conveyed to the outlet point of the drainage area.
Ail 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 mare slope values of particular
interest: I) average overland slope and 2) average charme] slope. Overland slope gives an
indication of how fast mno£f will travel on the land surface to a drainage channel, and charmel
slope relates how quickly the runoff will be routed to the outlet point of the drainage area.
Drainage areas within the City wpically 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 from 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 distal elevation model (DEM), a grid comprised of
10-meter ceils, 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
METHODOLOGIES
2.1.2 Soil Types
The types of soils present in a drainage area have a significant impact on the amount of runoff a
~ven 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 distal soils database in GIS. Soil survey SSI_TRGO and SATSGO databases
developed by the Natural Resources Conservation Service CNR. CS) were used. The SSURGO
data set was used ro provide specific information about each soil series within the drainage areas.
Because the major/fy of the soils in the Dubuque area are classified as hydrologic soil group 'B,'
the less detailed STATSGO database was used to ~tevelop hydrologic models° This information
was then combined with land use data to obtain hydrolog/c characteristics for each polygon.
2.2 URBAN DEVELOPHENT CHARACTERISTICS
2.2.! 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 charmels. The effect land use has
on water quamiry is generally hnked 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
rouglmess of the land. In general, an area with a high percentage of impervious area will have a
quicker t/me to peak and a higher peak, than a sim/far 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 persormel. The landuse categories within the drainage basins are
shown in Table 2.1.
City of Dubuque. Iowa
Methodologies 2-2
Drainage B~in Master Plan
Fall 2001
lvI ETHODOLOGIES
Table 2.1
Drainage Basin Land Use Groups
. Land Use GroUp ;
ST Streets
CO Commercial
IND Indus~at
/NS Institutional
HI) [ High Density Resident/al
M2D Medium Density Residential
LD Low Density Residential
AG Agricultural
OP Open Space and Grass
2.3 HYDROLOGIC hlODEL
The U.S. Army Corps of Engineers (USACE) Hydrologic Engineering Center (HEC) Hydrologm
Modeling System (HEC-HMS) was selected to model the drainage areas in the city of Dubuque.
HEC-H_MS simulates precipitation-runoff 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.
H~EC-HMS is designed to simulate the surface runoff response of a drainage basin to
precipitation input. The model represents the basin as an intemonnected system of hydrolo~c
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 model/rig is the
computation of stre.am flow hydrographs at desired locations in the drainage area.
NRCS methodology was used to determine runoff volumes, direct runoff and ctmrmel routing.
The advantage of the NRCS methodology is ir converges quickly, resulting m 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 N'RCS methodology was used.
City of Dubuque, Iowa Drainage Basin Master Plan
Methodolo~es 2-3 Fall 2001
METHODOLOGIES
Key data required by the HEC-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 roming 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 infiows to the conveyance sysmm,
By following the general guidehnes, 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.
Ci~ of Dubuque Iowa
Methodologies 2-4
Drainage Basin Master Plan
Fall 2001
METHODOLOGIES
2.3.2 NRCS Runoff Curve Number
The Natural Resources Conservation Service [NY. CS) runoff curve number procedure w~s used
to compute abstractions for storm rainfall. Absu-actions 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 d~pth of precipitation. The curve number is a function of Iand 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 ci~"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 di'ained 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 whet9 agricultural development was
present, the hydrologic analysis was performed as agricultural land use, because developers are
required to provide on-site detention to maintain existing runoffreleases.
Table 2.2
Drainage Area Land Use Groups and Curve Number
:~'I~ ad:~seGrouo. ~_ escrlpfion_~;
ST Streets 99
IND Indus~al 88
CO Commercial 92
INS Institutional 88
HD High Density Res/denfial 85
.MD Med/um Density Residential 75
LD Low Density Residential 72
AG A~mhculmral 73
OP Open Space and Grass 69
City of Dubuque, ]owe Drainage Basin Master Plan
Methodologies 2-5 FeE 2001
METHODOLOGIES
2.3.3 NRCS Unit Hydrograph
The unit hydro.apb method is the component in the rainfall-runoff model that transforms the
rainfall excess into a surface runoff hydrograph. The unit hydro,apb represents a typical
hydrograph shape for a drainage area. The unit hydrograph for a drainage area is defined as a
direct rtmoffhydrograph resulting from one inch of excess rainfall generated uniformly over the
drainage area at a constant rate for a storm ora specified duration.
The NRCS unit hydrogaph method relates hydro~aph characteristics to a physical characteristic
of the drainage area, the basin time to peak, tp. The basin time [o 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:
where:
[lag
time to peak, in hours
computational interval, in hours
tag time, in hours
The lag time is defined as the t/me 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:
L°.~(S +1)°-7
1900 yO.~
I000
S = -10
CN
where: [lag
L
y
CN=
lag time, in hours
g-reatest flow length, in feet
average drainage area slope, in percent
runoff curve number, based on land use, land treatment and soil
type
The N-RCS unit hydrograph method was utilized in the HEC-HMS model for the drainage basins
in the study.
City of Dubuque,
Methodologzes
Drainage Basin Master Plan
2-6 Fall 2001
METHODOLOGIES
2.3.4 Rainfall
The 24-hour rainfall depths for the I0-, 50-, 100- year frequency shown in Table 2.3 were based
on the point Istation) data and developed as isohyetal maps presented in the M/dwestern Climate
Center and Illinois State Water Survey publication, Bulletin 71, "RalnfalI Frequency Atlas of the
Midwest". The point data values are kigher than the area/mean relations determined for eac?,
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 nor used [o 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
R~i~urn Period
O-Year
' Rmnfall Depth (inches)
4.5
50-Year { 6.0
100-Year 7.0
500-Year 11.0
ha order to calibrate the hydrologic model, a comparison of the basha 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 sn:eam, so
synthetic methods were used to obtain the discharge-frequency relationships in the FIS. In
addition, the Iowa Department ofTransponation's (IaDOT) regression equations were compared.
A summary, of 100-year peak discharges is shown in Table 2.4.
City of Dubuque. ]owa Drainage Basin Master Plan
Methodologies 2-7 Fall 2001
METHODOLOGIES
Table 2.4
North Fork Catfish Creek Peak 100-Year Discharge Comparison
at Confluence with Middle Fork Catfish Creek
Dischai-~e
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-I-IMS 2,950 Existing land use conditions with no
effective storage. Type-II distribution.
HEC-I-IMS 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 FIS 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 hyerogaph for each basin was developed using a 15-minute time increment
and a modification of the NRCS Type-Il rainfall distribution by including the 6-hour rainfall
hyetograph within the 24-hour hyetogaph. Th/s technique maintained the depth and t/ming 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.
City of Dubuque. Iowa
Methodologies
Drainage Basin Master Plan
Fuji 2007
METHODOLOGIES
Table 2.5
City of Dubuque 15-Minute Time Distribution for 24-Hour Storm Event
0.010 0.014 0.018 0,03~ 8 ~
..... ~: 0.024 0.032 0.042 0.074
0.010 0.014 0.018 0.032 ' 0.024 0.032 0.042 0.074
;iJ25:1 0.010 0.014 0.018 0.032 ~ 9~25 : 0.028 0.036 0.058 0.085
1::5 0.010 , 0.014 0~018 0.032 9~5 0.042 0.056 0.063 0.085
1.75 0.010 10.014 [ 0.018 0.032 9.75 0.042 0.056 0.063 0.096
:2:~ 0.010 ~ 0.014 0.018 0.032 ~0 ' 0.046 0.061 0.068 0.096
] ~:~25. 0.010 0.014 0.018 0.032 :::t025 0.056 0.075 0.084 0.112
0.010 0.014 0.018 0.032 0.056 0.075 0.084 0.127
~ 75 ~:~; 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 I 0.032 0.095 0.127 0.142 0.223
0.010 0.014 0.018 0.032 0.119 0.160 0.179 0.276
0.010 0.0t4 0.018 0.032 0.193 0.259 0.28P 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 0A63 0.2~
0.014 0.018 0.024 0:042 :i:~ :5:' :~. 0.087 0.118 0.131 0.19I
0.014 0.018 0.024 0.042 0.077 0.I03 0.I16 0.159
~5':[' 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.I 17
0.0 4 0.0 8 0.0 4 0.04 o.os3 0.07 0.079 0. 06
::: ~25 0.017 0.023 0.030 0.053 :i~25 0.042 0.056 0.063 0.096
0.017 i 0.023 0.0B0 0.053 ;]. }~:S :2~' 0.042 0.056 0.063 0.085
0.017 0.023 0.030 0.053 0.042 0.056 0.063 0.084
o.o o
]¢~25 0.017 0.023 0.030 0.053 0.024 0.032 0.042 0.074
7.5 ~ 0.017 ~ 0.023 0.030 0.053 ~ ~1:5.5 :: 0.021 0.027 0.036 0.0~
7-g5 0.0t7 ~ 0.023 0.030 ~ 0.053 [ ~5;~5 :~ 0.02I I 0.027 0.036 0.0~
City of Dubuoue Iowa Drainage Basin Master Plan
Methodologies 2-9 Fall 2001
METHODOLOGIES
Table 2.5
City of Dubuque 15-Minute Time Distribution for 24-Hour Storm Event
;I6 .: ~':: ~0.021 0.027 0.036 0.064 20:25 0.010 0.014 0.018 0.032
,1.6.25 . 0.021 0.027 0.036 0.0~ :;, 20,~. .' "". 0.0t0 0.014 0.018 0.032
'~6.5 '~: 0.021 0.027 0.036 0.064 :'20.75 '.:. ' .~ 0.010 0.014 0.018 0.032
· .',~ &~5: .- 0.017 0.023 0.030 0.053 · ' 2 I:,.':'-':.:: - · · :: 0.010 0.014 0.018 0.032
:17.: ': 0.017 0.023 0.030 0.053 .21.25 0.0t0 0.014 0.018 0.032
17.25 0.017 0.023 0.030 0.053 21.5 0.010 0.014 0.018 0.032
17.5: 0.017 0.023 0.030 0.053 21.75 0.010 0.014 0.018 0.032
17.75 0.017 0.023 0.030 0.053 22 0.0t0 0.014 0.018 0.032
18 0.014 0.018 0.024 0.042 22.25 0.010 0.014 0.018 0.032
18.25 · 0.014 0.018 0.024 0.042 22.5 0.010 0.014 0.018 0.032
:'18:5::. -. 0.014 0.018 0.024 0.042 ::~22 75 · ~ 0.010 0.014 0.018 0.032
,18;75'.- 0.014 0.018 0.024 0.042 ::2J:::. ? 0.010 0.014 0.018 0.032
::~:~';~:'"- 0.014 0.018 0.024 0.042 2[::23.25::.::::: 0.010 0.014 0.018 0.032
~9.2'5 :: 0.014 0.018 0.024 0.042 ?~23~.5:," :~ 0.010 0.014 0.018 0.032
-~,9}5::.:/' 0.014 0.018 0.024 0.042 :: ':.23:,75::~:, :. 0.010 0.014 0.018 0.032
'..5¢:..75,'~: 0.014 0.018 0.024 0.042 .,';.2~.~2::.~::d:: 0.007 0.009 0.012 0.021
· 20 "{:~r:-;;:: 0.010 0.014 0.018 0.032 :T6~a~:~[,~::r 4.5 6.0 7.0 I1.0
2.3.5 Channel Routing
Pouring of flood flows from the outlet of an upstream subbasin to the next subbasin outlet was
accomplished using the Muskingum routing method in HEC-FfMS. 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 accoum for the flood attenuation effects
associated w/th roadway storage and existing and potential detention basins. The HEC-HMS
Modified Puls routing routines were used to simulate flow.g-a-ough the reservok~s using the leveI
Cizy of Dubuque, iowa
Methodologies 2 - ] 0
Drainage Basin Master Plan
Fail 2001
METHODOLOGIES
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-outfiow relationship and combining it with the stage-storage
relations?tip for the upstream reservoir pool. The stage-storage relationskip was derived fi.om
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 homographs comained in the Federal Highway Administration's (FHWA)
Hydraulic Deaigau Series No. 4 (HDS-4).
2,3.7 CRWR-PrePro
A preprocessor was developed by the Center for Research and Water Resources (CRV/R) at the
University o£Texas, Austin, under the supervision of Dr. David Maidmem. 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-H2'vlS is currently being developed by HEC as
part of the NexGen program of research. The purpose of CRWR-PrePro is to summarize data
~om a GIS system for input to HEC-HMS. CRWR-PrePro uses stream and subbasin GIS layers
as input data. S~eam and subbasin data layers are required as input, and the sofc,vare requires
the use of metric un/ts. The CRWR-PrePro analysis was executed usmg metric units and then
the output data, consisting of a HEC-H2MS 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 pro,am code is oriented around identifying hydrolo~c elements and the relationship
between these elements. Seven (7) hydrologic elements are identified: subbasins; sources;
reaches; junctions; rese,woirs; diversions and sinks.
The step-by-step methodology for developing a H~C-E12ViS basin file using CRWR-PrePro is
presented below. These steps produce a HEC-HMS baain file, wkich is then Lmported into HEC-
HMS.
city of Dubuque, ]oven Drainage Basin Master Plan
Methodologies 2-] 1 Fall 200]
METHODOLOGIES
Table 2.6
Spatial Data for CRWR-PrePro
Data Set ~
DEM
Digital elevation model (DEM), I 0 meter grid of elevations describing
topo~aphy, developed from the DigimI Terrain Model (DTM) within the
DAGIS dataset.
Rf Shape file of streams or reaches developed by the EPA, aug~nented by
DAGIS data.
LU Land use shape file developed from DAGIS data.
STATSGO Stare Soil Geo_m'aphic database, soil classifications, developed by U.S.
Geolog/c Surv'ey
~1 Aerial photo~aphy used for identifying structures and other features.
Aerial
Photos
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 m assure the streams delineated fi-om
the DEM match those from the EPA reach file (P,2).
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 ceils draining To each
point.
6. Construct a stream network based on a user defined accumulation threshold.
7. Streams may be added to ~e stream net~vork 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 ~vhere necessary (i.e. at s~rucmres).
11. Delineated drainage areas from each of the outlets using the DEM.
12. Streams and drainage area grids are converted to vector shapeffies.
13. Subbasins may be merged.
14. Calculate runoff curve numbers based on Iand use and soil classification.
15. Determine lag time based onbas/n topography.
16. Determine Muskingum coefficients based on charmel characteristics.
City of Dubuque. Iowa Drainage Basin Master Plan
Methodologies 2-12 Fall 2001
METHODOLOGIES
17. Export the data set to a HEC-HMS basin file.
18. Import the HEC-t-LMS 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 dra/nage structures. Peak runoff rates computed as part of the hydrologic modeling
were used in conjunction with the GIS and 1/mited 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. return period flood events. The resulting 100-year floodplain for
ultimate development w/th 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 I00-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 - R/ver 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
netwofr of natural and constructed open channels. The £ollowing 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 superc15t/cal flow characteristics, it ~s
conservative to base the hydraulic analyses on subcriticaI flow, since the depth of flow for
subcritical flow conditions is greater than supercrifical flow conditions.
XP-SW'MM was used to analyze closed conduit hydraulics. XP-SW'MM is proprietary s~orm
water modeling sofavare based on the U.S. Environmental Protection Agency model SWMM
(Storm Water Management Model). XP-SWMM is capable ofmodeling unsteady flow allowing
for analysis of changes in flow variables w/th t/me and attenuation of peak discharges as a resuh
CiD of Dubuque, Iowa Drainage Basin Master Plan
Methodoloo~es 2-I3 Fall 2001
METHODOLOGIES-
of storage. The following assumptions are used in hydraulic computations performed by XP-
SWivLM:
Gradually varied flow;
· One-dimensional flow; and
· Subcfitical flow
2.4.1 Model Schematic
For the open channel model, channel cross-section geometry and flow lengths were obtained
from a triangular irregular model (TD0 developed from the distal terrain model 0DTM). Cross-
section geometry was generated from the TIN and the U.S. Army Corps of Engineer's I-IEC-
GeoP,-~.S software in conjunction with ArcView's 3D-Analyst which electronically generates the
HEC-RAS input files within ArcVie~v. Bridge and culvert geometry were obtained from field
measurements. Manrfing'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 rou~mess 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. Marming'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 return 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 converfienr method for analyzmg a range of channel improvemem options
and includes computational procedures for estimating excavation volumes and computing
City of Dubuque. iowa
Methodo lo~mes 2-14
Drainage Basin Master Plan
Fall200]
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.
All policies of insurance required hereunder shall be endorsed to provide a thirty
(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 cop~es of the endorsements set forth in Paragraphs 2
and 5 to evidence inclusion in the policy, shall
also be required to ~rovide Certificates of Insurance of all subcontractors, and all
sub-subcontractors who perform work or services pursuant to the provisions of
this contract. Said certificates shall meet the same insurance req Jirements as
are required of
Each Certificate of Insurance shall be submitted to the contracting department of
the City of Dubuque, Iowa prior to commencement of work/service. (The
contracting department shall submit the certificates to the Finance Director.)
All 3olicies 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 mmunities Endorsement.
Failure to provide evidence of minimum coverage shall not 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 all sub-subcontractors
shall be required to carry the following mimmum insurance coverages or greater
if required by law or other legal agreement:
PROFESSIONAL LIABILITY:
$1,000,000
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
$ 2,000,000
$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:
$1,000,000
' To be determined on a case-by-case basis by Finance Director.
RevisedJanuary, 2002
POLICY NUMBER COMMERCIAL GENERAL LIABILITY
THIS ENDORSEMENT CHANGES THE POLICY. PLEASE READ IT CAREFULLY.
ADDITIONAL INSURED - DESIGNATED PERSON OR
ORGAN IZATION
This endorsement modifies insurance provided under the following:
COMMERCIAL GENERAL LIAaiL[TY COVERAGE PART.
SCHEDULE
Name of Person Or Organization:
The City of Dubuque, including all its elected and appointed officials, all its employees and volunteers, all
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.)
WHO IS AN INSURED (Section Il) is amended to include as an insured the 3erson or organization shown
in the Schedule as an insured but only with respect to liability arising out of your operations or premises
owned by or rented to you.
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.
o
~ The insurance carrier further agrees that this policy of insurance
shall cover only those claims not subject to the defense of governmental immunity
under the Code of Iowa 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 Imm~mity, The City of Dubuque, Iowa shall be responsible
for asserting any defense of governmental immunity, and may do so at any time and
shall do so upon the timely written request of the insurance carrier.
Non-Denial of Coverage, The insurance carrier shall not deny coverage under this
policy and the insurance carrier shall not deny any of the rights and benefits
accruing to the City of Dubuque, Iowa under this policy for reasons of governmental
immunity unless and until a cour[ of competent jurisdiction has ruled in favor of the
defense(s) of governmental immunity asserted by the City of Dubuque, Iowa.
No Other Change in Policy. The above preservation of govemmentaf immunities shall
not otherwise change or alter the coverage available under the policy.