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FLOOD MITIGATION
PROJECT
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Dubuque
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GREEN ALLEY
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The Bee Branch Watershed Flood Mitigation Project
The purpose of the Bee Branch Watershed Flood Mitigation Project is to prevent flooding,
improve water quality, stimulate investment, and enhance quality of life within the Bee
Branch Watershed. This $179 million, 12 -phase, 20 -year infrastructure project represents a
multi -faceted approach to addressing the severe and frequent flash flooding experienced in
the watershed.
Bee Branch Watershed
The combined phases will:
• reduce the volume of stormwater,
• slow the rate of stormwater through the upper
watershed,
• increase the safe conveyance of stormwater
through the flood -prone area, and
• provide floodwater protection to the City's
water treatment plant on Hawthorne Street.
Impervious Surface Reduction (Green Alleys)
The "Impervious Surface Reduction" phase of the project focuses on reducing the volume of
stormwater in the watershed. An impervious surface does not allow rain water to soak into the
ground. Examples include traditional concrete, asphalt, and packed gravel surfaces (driveways,
alleys, sidewalks) as well as rooftops. By reducing the amount of impervious surfaces in the
watershed, more stormwater can soak into the ground instead of creating excessive run-off that
can exceed the capacity of the storm sewer system during major rain events. Pervious surfaces
also reduce pollutants on the roadways from running off into the storm sewer system and ultimately
the Mississippi River. In short, the goal of impervious surface reduction is to reduce the volume
of stormwater contributing to flooding by allowing it to soak into the ground.
An example of a completed Green Alley
in Dubuque
Interlocking pavers allow water to infiltrate
into the soil below.
The main way impervious surface reduction will be achieved in the Bee Branch Watershed Project is by converting
approximately 240 alleys to "green alleys." Green alleys feature a special permeable pavement surface. For this
project, specially designed interlocking concrete pavers will be utilized. The surface has openings or pores that allow
water to pass between, or infiltrate, the pavers and percolate through two to three feet of stone aggregate and then into
the soil below. The alley is also "pitched" or graded to allow water that does not soak in to run to the center of the alley,
flow to the street, and then into the storm sewer system.
C'SUSTAINABLE
DUBUQUE
viable • livable • equitable
The City of Dubuque's Green Alley program supports the Sustainable Dubuque principles of
Clean Water, Community Design, and Community Health & Safety
More About Green Alleys
The goals of converting the existing alleys in the watershed to green alleys are to
prevent adjacent properties from flooding, reduce the rate and quantity of stormwater
runoff throughout the watershed, recharge/replenish the ground water, and filter soil,
pollutants, and debris.
Permeable/green alleys are being used successfully throughout the country and were
tested in several downtown Dubuque locations before being selected for the Bee
Branch Watershed Project. Other communities using permeable surfaces to address
stormwater management include: Charles City and West Union, Iowa; Chicago, III.; St.
Louis, Mo.; Seattle, Wash.; and Portland, Ore.
Permeable pavement allows
infiltration of air and water
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Approximately 240 alleys in the watershed will be converted to green alleys over the course of the 20 -year project with
approximately 75 completed from 2014-2017. This conversion to pervious surfaces is expected to reduce stormwater
runoff within the watershed by up to 80%.
Alley Drainage Improvement through Proper
Alley Pitching and Grading
Alley surface is properly
pitched and graded to direct
runoff into the center of the
alley
Energy efficient/
dark sky lighting
Private driveway
apron
Alley righ
Project Funding
The total cost for the Bee Branch Watershed Flood Mitigation
Project, excluding interest on debt, is just over $179 million.
The project funding includes federal, state, city and special
assessments to property owners. The impervious surface
reduction (green alley) phase is expected to cost $57.4
million.
In early December 2013, the City was awarded $98.5 million
from the Iowa Flood Mitigation Board for the project in the
form of state sales tax increment financing. These funds are
Alley driveway
apron
Runoff is collected by the
existing sewer system
All alleys, whether they are permeable or not, should be properly
graded and pitched to allow water to run to the center of the alley
and then flow to the street. This prevents the need for additional
sewer infrastructure and prevents adjacent properties from flooding.
based on increases to local state sales tax revenue and are
made in annual payments spread over the next 20 years.
When combined with other state and federal grants and local
donations for the project, the City has received over $127
million to help fund the $179 million project.
As with most projects funded in part by state and federal
programs, a "local match" is provided. In this case,
Dubuque's local match includes stormwater utility funds and
special assessments to property owners.
Special Assessments
Whenever the City reconstructs a street or alley, the abutting property owners are assessed a portion of
the cost, usually approximately 15% of the actual cost. The remainder of the cost (85%) is covered with
city funds or grant funding. The reason abutting property owners receive an assessment for the project is
because they also receive a corresponding benefit of the project that the rest of the citizens are not receiving.
The benefits include reduced flooding and icing, an improved road surface, and better access to property.
The assessment to a particular property is proportional to the size of their lot/property.
The assessment amounts will vary based on the frontage (width) and depth of the lot. For most of the alleys in the
Bee Branch Watershed, an approximate "rule -of -thumb" cost of the assessment to the property owner will be $21
per foot of frontage. For example, if you have a 50 -foot -wide lot, the approximate assessment could be calculated by
multiplying $21 times 50 for an assessment of $1,050. However, it is important to note that these costs are influenced
by the contractor's bids and whether or not there are cost overruns during construction. A preliminary assessment
notice will be sent to all property owners before a public hearing with an estimate of the assessments at a City Council
meeting. That number represents a "worst-case scenario" and includes additional costs for possible overruns and
engineering costs. Most final assessments for average -sized lots are expected to be in the range of $800 to $1,000.
Financial Assistance
The City of Dubuque offers financial assistance for owner -occupied
properties along the green alley being replaced. For example:
A household of four with a total household income of
$45,000 would receive 50% off of their assessment
A household of two with a total household income of
$40,000 would receive 34% off their assessment
A household of one who makes less than $19,000 a
year would receive 100% off their assessment
Sample Income Guidelines
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Whether a household qualifies
for financial assistance or not,
there is the option of financing
the assessment over a period
of 15 years at 3% interest. See
payment example below:
Assessment
$800
$1,000
Monthly Payment
$5.60
$7.00
Family Size Income Limit % Relief
1 $38,850 20%
$31,566 50%
$24,282 80%
$19,425 100%
2
$44,400 20%
$36,075 50%
$27,750 80%
$22,200 100%
3
$49,950 20%
$40,585 50%
$31,219 80%
$24,975 100%
For a complete list of income guidelines, visit www.ciiyofdubuq
Family Size
4
Income Limit % Relief
$55,500 20%
$45,094 50%
$34,688 80%
$27,750 100%
5
$59,950 20%
$48,710 50%
$37,469 80%
$29,975 100%
6
$64,400 20%
$52,325 50%
$40,250 80%
$32,200 100%
ue.org/beebranch or call 563.589.4270.
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How long will the construction last? Alleys
that do not contain water and sewer
utilities will each require about a month
to reconstruct, depending upon weather.
Alleys that do contain sewer and water
utilities could take a month and a half to
two months to reconstruct. The City and the
contractor will work with abutting property
owners to facilitate access to garages
and the rear of properties for as long as
possible. It is anticipated there will be two -
to three-week timeframes where access is
prohibited to facilitate the installation of
the pavement or utility.
My property doesn't flood and the water from
our alley all soaks into the ground now. Why
is my alley being reconstructed? All alleys
and other impervious surfaces throughout
the watershed contribute to the flooding
problems throughout the watershed. When
stormwater runs off your property, it enters
the street and storm sewer system. The
capacity of the system can be exceeded
in major rain events. The project takes a
comprehensive, watershed -wide approach
to reducing the amount of stormwater
that enters the system and to increase
the capacity of the system to prevent
flooding and private property and public
infrastructure damage.
Where can I park during construction? During
construction, abutting property owners
will need to utilize available on -street
parking or make other arrangements with
neighbors to park. The City understands
this is inconvenient for the short term. The
contractor will try to facilitate access to
abutting properties for as long as possible.
Where will my trash, recycling, and yard
debris be picked up during construction? If
these collections are made in your alley, you
will have to place the materials out on the
street, instead of the alley for a period of
time. You will be notified when this will be
necessary.
What will happen to my landscaping/
flowers near the alley? Because the right-
of-way (ROW) is not private property, any
landscaping in the ROW is subject to
disturbance. The City and the contractor
will work with the adjoining property owner
to try and minimize disturbance when
possible. However, any trees and shrubs in
the right of way are subject to removal by
the City.
What if my driveway and/or sidewalk connects
to the alley? When constructing the green
alley, the City will transition the pavement
so that existing driveways and sidewalks
are accounted for. If the existing driveway
is gravel, the City will construct a concrete
apron that extends to the property line.
If the driveway is paved, the City will
transition to the paved driveway/sidewalk as
far as the property line. Any improvements
requested beyond the property line will be
the abutting property owners' responsibility.
Who owns alleys? All of the alleys in this
project are in the public (City -owned) right-
of-way (ROW), an area owned by the City
to allow for the installations of utilities and
roadways.
Will there be ice in the alley? There will be
situations where ice will build up in alleys,
but likely less than a traditional surface.
The new permeable pavers will help reduce
the ice, especially if the winter season has
the freeze/thaw cycles Dubuque usually
experiences. The stone aggregate beneath
the pavers allows water to infiltrate even in
the winter months.
Will the pavers settle or shift? By design,
the pavers will initially settle about a half
inch. They are installed with this initial
settlement in mind. Additional settling or
shifting is minimal because concrete collars
or bands are installed along the edge of
the alley to hold the pavers in place, and
because of the significant amount of clean
stone aggregate underneath the pavers.
Questions or comments about this project?
Written comments can be submitted to the City Clerk's Office, the
Engineering Department, City Manager, or your City Council representative.
The Green Alley project contact in the Engineering office is: Jon Dienst, P.E.,
Civil Engineer, jdienst@cityofdubuque.org, 563-589-4270.
These are engineered pavement systems
and perform much better than the current
patio pavers used today and the old brick
streets from years ago.
What type of maintenance will the City
provide in the future? The City will provide
for regular alley sweeping and vacuuming
in order to maintain the permeable nature
of the pavers. Additionally, the City will
replace loose or broken pavers if they
should occur. The City will not plow alleys
in residential neighborhoods.
Will stormwater be diverted through my
property? The Green Alley project is not
intended to divert water through your
property. However, if the natural lay of
the land currently has water running
through your property, Iowa law requires
you to continue to accept that water. The
permeable pavements of the alleys should
reduce the runoff that may travel through
your property.
Will the Green Alleys eliminate street
flooding? No. Streets are designed to
convey stormwater, as well as vehicles. It
is standard engineering practice to design
a street to carry half a lane's width of water
during significant storm events. However,
other phases of the flood mitigation project
are designed to increase the capacity of
North End storm sewers and streets to
help reduce the street flooding that can
sometimes occur.
Are Green Alleys a beautification project?
No. The Green Alleys are a stormwater
management and water -quality project.
The fact that the alleys look attractive is a
bonus.
To receive email and/or text 1
message alerts regarding the
Bee Branch Watershed Flood
Mitigation project, visit
www.cityofdubuque.org/notifyme
For more information on the
project, including videos, visit:
www.cityofdubuque.org/beebranch