Stormwater Mgm Pl Ltr 12 11 01CITY Of DUBUQUE, IOWA
MEMORANDUM
December 11,2001
TO:
FROM:
SUBJECT:
Michael C. Van Milligen, City Manager
Gus Psihoyos, Assistant City Engineer
Deron Muehring, Civil Engineer ~
Stormwater Management Plan
INTRODUCTION
The attached resolution provides for:
1)
2)
Adoption of the City of Dubuque Drainage Basin Master Plan (DBMP)
prepared by HDR Engineering, Inc.; and
Authorization to prepare a Request for Proposals (RFP) for a corridor
study to establish the alignment of the Bee Branch basin flood control
channel recommended in the DBMP.
BACKGROUND
In '1996, the City of Dubuque, through the Capital Improvement Project Budget,
committed to developing a City-wide Stormwater Management Plan. The need
for the plan arose from a growing number of citizen complaints related to
stormwater runoff, increasing public safety and reducing property damage are
the primary goals of the Stormwater Management Plan.
1997, six consulting engineering firms formally submitted proposals tp prepare
plan for the City. After a second interview the team of engineers headed by
HDR Engineering, Inc. of Omaha, Nebraska was selected to produce Dubuque's
Stormwater Management Plan.
The Stormwater Management Plan consists of four elements:
A Drainage Basin Master Plan that addresses flooding problems
and issues in specific watershed basins;
A Stormwater Drainage Criteria Manual that guides development to
prevent new drainage problems and reduce pollution associated
with stormwater runoff;
A set of ordinances and policies that specifically address
stormwater runoff issues; and
A skeleton NPDES Phase Il permit application to be refined by City
Staff.
The accompanying document is the Drainage Basin Mater Plan, prepared by
HDR Engineering, for the Bee Branch and North Fork Catfish Creek watersheds
(see Figure 1). It should be emphisized that the Drainage Basin Master Plan
does not identify all areas within the City that experience poor drainage. In fact,
many drainage problems are of a localized nature: The City will continue to
investigate all drainage complaints on an individual basis, assess whether the
master plan addresses such issues, and assist property owners in any way
possible to reduce the impacts of stormwater runoff. The remaini'ng tasks will be
completed during the winter of 2001-2002.
DISCUSSION
A master plan is a plan for an entire watershed. When a modification is made to
a portion of a watershed's drainage pattern it usually effects, for better or worse,
the drainage of the entire Watershed. The Drainage Basin Master Plan is
necessary to ensure that efforts to solve stormwater problems are efficient and
cost-effective and address the concerns of taxpayers and drainage system users.
To achieve the primary objective-increasing public safety and reducing property
damage related to stormwater runoff-the following steps were followed:
1. Determine the capacity of the existing drainage system for the 10-,
50-, 100- and.500-year return period storm events under future
drainage basin characteristics;
2. Develop hydrologic and hydraulic models suing aerial topographic
mapping using the Dubuque Area Geographical Information
System (DAGIS) for major drainage segments within each
watershed;
3. Identify areas where public safety is compromised and property
damage occurs due to stormwater runoff;, and
4. Identify funding sources that might be available to construct the
recommended drainage improvements identified by the Basin
Master Plan.
North Fork Catfish Creek Basin Plan
Several problem areas were identified within the North Fork Catfish Creek
drainage system. Figures 3-14, 3-15, and 3-16 in the Drainage Basin Master
Plan outline the flooding extents under existing and proposed conditions. The
benefit of the recommended improvements (alternative 2) is reflected by the
proposed conditions. Outlined in Table 1 is the $2,135,300 worth of
improvements recommended, and the order in which they should be constructed.
2
Figure 2. lO0-year floodin~ depths under existin~ conditions.
Washinton Street Sub Area 100-yr Flood Inundation
Existing conditions flooding depths (feet)
0.1-0.5
~1-2
~J 2 - 3
~j 3-4 N
1000 0 1000 2000 Feet
Alternatively, it was discovered that an open channel originating at 24th and Elm
Streets and extending to the 16th Street detention cell would eliminate the risk of
flood damage to the remaining 970 homes and businesses. Therefore, the
Drainage Basin Master Plan recommends the construction of the open channel.
The cost of the channel, which includes the purchasing of approximately 70
homes/businesses, is estimated at $17.1 million. Figure 4 shows the channel
extents.
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Prepared by Deron Muehring, Civil Engineer
Cc: Barry Lindahl, Corporation Councit
Cindy Steinhauser, Assistant City Engineer
Pauline Joyce, Administrative Services Manager
Ken Tekippe, Finance Director
Mike Koch, Public Works Director
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