Underground Wet Ponds for Stormwater Management in Wisconsin

Wet Ponds
a Contech Solution for Stormwater Management
A compilation of case studies
highlighting the advantages of a wet
pond solution provided by Contech
Engineered Solutions that will meet
(and sometimes exceed) the TSS
mandates stipulated by the Wisconsin
Department of Natural Resources.
2012 | www.ContechES.com/UrbanGreen
Stormwater Solutions from Contech®

www.ContechES.com/UrbanGreen 2
Table of Contents
Check out more »
stormwater management
solutions provided by
Contech Engineered Solutions
at www.ContechES.com/urbangreen
Stormwater Solutions
The Contech fit with WINSLAMM for TSS Removal| 4
Underground Wet Ponds
Modeling Options| 5
Wisconsin Project List | 5
Case Studies
Sacred Heart Senior Apartments » Saint Francis, WI | 6
Redevelopment at Main Street & Pilgrim Road » Menomonee Falls, WI | 8
Boucher Automotive Group » Franklin, WI | 10
© 2012 Contech Engineered Solutions LLC

A Stormwater Solution for Wet Ponds
Contech fits WINSLAMM for TSS Removal
with their Underground “Pond”
Wet Ponds
Wisconsin Department of Natural Resources (WDNR) mandates that
New Development projects reduce Total Suspended Solids (TSS) by
80% and a 40% TSS reduction for redevelopment projects. One
option is to construct a Wet Pond with a permanent pool of water.
However, for most urban-set projects this is not an option due to
limited land resources. Contech’s economical solution to meet the
WDNR TSS removal requirements is to construct “Underground Wet
Ponds” using metal, plastic and concrete systems. The lower portion
of the pipe contains a permanent water pool to remove TSS while the
upper half of the pipe can be used for Active Storage if needed. With
the “Pond” underground the land can be utilized for other uses, most
often parking.
Interested in learning more? We’d love to hear from you!
» Eric Sturm | Project Consultant
(608) 215-3937
esturm@conteches.com
» Todd Riebau | Project Consultant
(608) 576-0109
triebau@conteches.com
» Keith Johnson | Sales Engineer
(920) 860-0989
kjohnson@conteches.com

Wet Ponds
Underground Wet Ponds
Modeling a Contech System in WINSLAMM
Underground
Wet Ponds can be
modeled two ways
in WINSLAMM:
1 Catch Basin
After entering the necessary project parameters, alter
the catch basin size until the TSS removal rate meets
or exceeds the project requirements. The screen
shots to the right illustrate a project in the Milwaukee
area, one acre of impervious area and a 40% TSS
removal requirement. After a couple iterations in
the catch basin routine, WINSLAMM determined that
266 sf of surface area is required. This equates to
38 lf of 84” dia. CMP with a 3.5’ deep permanent
water pool. Another option would be to use 47’ of
72” dia. CMP with a 4’ pool.
2 Treatment/Detention System as a Pond
The majority of the projects that Contech Engineered
Solutions has been involved with require either a
3.5’ or 4’ permanent water pool. Three feet of
permanent water pool for particles to settle out of
solution and a 0.5’ to 1’ sediment collection area.
We have the experience to prove it. Here are a few examples!
» Johnson Bank | Brookfield
» UW Credit Union| West Allis
» Walmart | Menonmonee Falls
» West Milwaukee | West Milwaukee
» Walmart | South Milwaukee
» Wisconsin Veterans Home | King
» CVS Pharmacy | De Pere
» Cabela’s | Ashwaubenon
» Boucher Automotive | Franklin
» Sacred Heart | St. Francis
» Oshkosh Correctional | Oshkosh

Case Study for Underground Wet Ponds
Sacred Heart Senior Apartments
Saint Francis, Wisconsin
Project Team Members:
Owner:
Sacred Heart of Jesus Parish
Engineer:
The Sigma Group
Contractor:
A.W. Oakes & Son
Technical Description:
CMP Detention 644-ft. of 142-in. x
91-in. CMP
Installation Date: August 2011
The Sacred Heart of Jesus Church, originally built in the
early 1960s, was renovated to include a new senior living
apartment community. The community, called the Sacred
Heart Senior Apartments, is a non-denominational facility
and seniors of all faiths are welcome.
The renovated sanctuary and rectory are 19,058 sf of the
113,735 sf project. The apartments occupied 84,081 sf in
the renovated space above the church, which were formerly
school classrooms, and also in the newly-built addition on
what was parking lot. There also is a 10,595 sf common
room shared between church and apartments
“We’re trying to reinvent ourselves,” said Eric Stemwell,
Sacred Heart Parish Core Team. “It’s kind of an experiment,
teaming up with a developer to offer senior housing. Senior
citizens are a very vital part of any community. What we’re
trying to do is create an environment where senior citizens
can thrive.”
The church contacted The Sigma Group of Milwaukee to
design the civil portion of the project which included the
stormwater management plan for the site.
The state Department of Natural Resources (DNR) requires
Total Suspended Solids(TSS) reduction in stormwater
leaving the site of 80% for new developments and 40%
for redeveloped projects. The 4.0-acre senior apartment
complex project was considered partially new development
and partially redevelopment; resulting in a weighted TSS
reduction requirement of 50%.
Because the project was located in an urban setting, The
Sigma Group did not have the option of an aboveground
5 www.ContechES.com/UrbanGreen
stormwater pond for the required TSS removal. Instead, they
looked at “mechanical” options that would be contained
beneath the parking lot.
The Sigma Group contacted Contech Engineered Solutions
for assistance in providing an economical solution to meet
the DNR requirements. The project covered 4.0 acres. Of
that, 2.83 acres were treated and 1.17 acres were taken
offsite with 0% removal. Contech proposed an underground
stormwater detention system utilizing corrugated metal pipe
(CMP) to treat the 2.83 acreage because it could achieve
the weighted 50% TSS reduction requirement. This solution
also met all of the project requirements while keeping within
budget.
Utilizing WinSLAMM (Source Loading And Management
Model for Windows) to evaluate sediment loading of
the project site, the Sigma Group determined that the
underground system needed 7,390 sf of surface area at the
water line and 48,035 cf of active detention storage.
The CMP detention system was constructed out of 644 feet
of 142-in. x 91-in. CMP coated with aluminum to fulfill
the surface area and active storage area requirements.
Aluminized, ALT2 coating was chosen to meet the 75 year
service life required by the owner. The system was designed
with a 3.5’ permanent pool of water in a serpentine
configuration to maximize the settling time. The calculated
TSS removal rate from Contech’s “underground wet pond”
solution was 76.61% - resulting in a net TSS removal of
56%, greater than the 50% required, for the entire 4.0 acre
site.

Site Designation » 142x91 Underground Storage | Saint Francis, WI
Sacred Heart of Jesus
Senior Apartments
Take a Deeper Look, Download the Standard Detail for this Project:
http://www.conteches.com/Site-Management/Document-Management.aspx?Command=Core_Download&EntryId=13288

Redevelopment at Main Street & Pilgrim Road
Menomonee Falls, Wisconsin
Owner:
Gatlin Development Co. Inc.
Engineer:
R.A. Smith National, Inc.
Contractor:
D. F. Tomasini Contractors, Inc.
CMP Detention 600-ft. of 108-in. dia.
Aluminized CMP
Installation Date: February 2012
A $10 million development anchored by a Walmart
Neighborhood Market Store, their smaller grocery format,
in the Village of Menomonee Falls, Wisconsin. Construction
design for this 40,000-sf Walmart and separate 5,000-
sf building for other retail tenants included a stormwater
management plan.
The Wisconsin Department of Natural Resources (WDNR)
requires total suspended solids (TSS) reduction in stormwater
leaving the project — 80% for new developments and 40%
for redevelopments. The 9.22 acre Walmart project was being
constructed on the site of a closed supermarket, making this
a redevelopment. Additionally, the flow rates for stormwater
leaving the site needed to be addressed.
Walmart contacted R.A. Smith National of Brookfield, WI,
to design the civil portion of the project, which included the
stormwater management plan for the site. Because this project
is in an urban setting, R.A Smith National did not have the
option of an aboveground stormwater pond for detention and
TSS removal. Instead, they looked at economical “mechanical”
options to contain stormwater beneath the parking lot to reduce
the footprint and maximize land use.
“Due to the dense redevelopment plan and the need to provide
water quality, it was apparent that the only way to achieve our
goals was to go with an underground facility”, said project
engineer Jeremy Jeffery of R.A. Smith National.
R.A. Smith National chose a corrugated metal pipe (CMP)
detention and treatment system from Contech Engineered
Solutions to satisfy the runoff release rates and TSS removal
requirements set forth by the Village of Menomonee Falls, the
Milwaukee Metropolitan Sewerage District and the WDNR.
“The Contech design proved to give us the most bang for
the buck,” said Jeffery. “We were looking for a product that
would provide the smallest footprint, superior durability and
service life, and easy installation, all while being cost-effective.
But the most important of all — a product that would meet all
regulating agencies requirements.”
The underground wet detention facility from Contech consisted
of 600-feet of 9-foot diameter Aluminized Type 2 (ALT2) CMP
pipe interconnected by a header. The bottom four feet of pipe
remains wet, and the top five feet were designed for stormwater
storage, allowing a 21,422-cubic-foot volume to reduce the
runoff release rate by more than 20% from the original rate for
both the 2-year and 100-year events.
Site water quality is attained by directing watershed to the
underground wet detention system. The bottom four feet of
the underground detention system functions as a large wet
sump with a permanent wet pool area. The wet pool area was
modeled in WinSLAMM (Source Loading And Management
Model for Windows), and designed to settle particles and
provide volume for sediment storage. To meet the WDNR’s
40% TSS removal requirement, a total of 1,359 pounds
of sediment removal was required. The underground wet
detention system removes 1,086 pounds, more than a 60%
removal rate. Six Catch basins with two-foot sumps were
designed for a second drainage area to remove an additional
275 pounds, allowing a combined total 1,361-pound TSS
removal, which exceeded the 40% WDNR requirement.
Contech’s underground wet pond detention and treatment
system reduced peak runoff rate and met the sediment
collection needs for the project, while keeping the project within
budget.

Site Designation » Ø108” CMP Detention | Menomonee Falls, WI
Redevelopment at Main Street
at Pilgrim Road – Walmart
Image © 2012 Google ∫ Map Data © 2012 Google

Boucher Automotive Group
Franklin, Wisconsin
Owner:
Engineer:
Site Engineering Services
Contractor:
D. F. Tomasini Contractors, Inc.
CMP Detention 800-ft. of 72-in. dia.
Aluminized CMP
CMP Treatment 23 & 44-ft. of 84-in.
Aluminized CMP
Installation Date: February 2012
A Milwaukee native, Gordon Boucher began his automotive
career in 1956 in sales for a local dealership. In 1977,
Boucher opened his first Lincoln-Mercury store, and ultimately
grew to own 16 southeastern Wisconsin dealerships. To
showcase additional inventory, Boucher wished to expand his
Franklin dealership, but expansion couldn’t be complete without
addressing state stormwater regulations. Boucher contacted
Site Engineering Services of Hartland, WI, to design the site
stormwater management plan and project.
The Wisconsin Department of Natural Resources (DNR)
mandates that redevelopment projects require a 40% Total
Suspended Solids (TSS) reduction in the stormwater leaving the
project. With the urban-set project and Boucher’s direction to
expand the parking area for at least 200 cars, an aboveground
TSS removal pond was not an option. To further complicate
matters, the site layout was long and narrow, with a steep
cross-slope in the middle.
“The whole point of the expansion was to gain parking for at
least 200 cars,” said project engineer Martin Worden of Site
Engineering Services, referring to the challenging layout of the
2.51-acre site. “We were really struggling to fit everything the
client needed on this narrow parcel of land.”
Underground pipes to store stormwater using catch basins for
the stormwater quality were considered. When the number of
catch basins grew to 26, it was evident another solution was
needed.
Site Engineering Services contacted Contech for an economical
solution that met DNR requirements. Contech proposed using
corrugated metal pipe (CMP) to create an underground water
detention with two treatment systems designed to imitate
the bay of a wet pond to conform with the DNR technical
standards.
“We knew we had to find another solution. The large diameter
Contech pipe was that solution,” said Worden. “Two sections
of 84-in. diameter pipe totaling 67-ft. in length replaced the
26 five-foot-diameter catch basins, and restored sanity to the
design.”
Two treatment systems were selected to minimize the collector
pipe use, and were designed with a 3.5-ft. -deep permanent
water pool that acts as a pond to capture sediments that wash
off the proposed parking lot. To maximize settling time, the inlet
and outlet pipes were placed on each end of the treatment
units. Another benefit of the detention system was its ability to
reduce the flow of water leaving the site.
Utilizing WinSLAMM (Source Loading And Management Model
for Windows) to evaluate sediment loading of the project site,
Site Engineering Services determined the treatment systems
needed 161 square feet of surface area for the north 0.68
acres and 308 square feet for the south 1.83 acres at the
spring line of the CMP. The detention system was constructed
out of 800-ft. of 72-in. dia. CMP to meet the requirement
for 25,452 cubic feet of active detention storage, while the
treatment units were constructed out of 84-in. dia. CMP. The
23-ft. north unit achieved 45% TSS removal rate, and the 44-
ft. south unit achieved 42%, both greater than the 40% state
DNR requirement. Aluminized Steel Type 2 (ALT2) coating was
chosen to meet Boucher’s required 75 year service life.
“In order to build a pond, we would have needed lots of
retaining walls around it,” Worden said of the long, narrow
project site. He said the Contech detention and treatment
system is “more competitive price wise.”
Contech’s “underground wet pond” solution, designed using
the ALT2 CMP detention and treatment systems, met all state
design requirements and the owner’s specifications, while
keeping the project within budget.

Site Designation » Ø72” Underground Detention | Franklin, WI
Image © 2012 Digital Globe, GeoEye, U.S. Geological Survey ∫ Map Data © 2012 Google

Site Designation » Ø48” CMP Underground Detention | De Pere, WI
CVS Pharmacy Store

Site Designation » Ø78” CMP Underground Detention | Oshkosh, WI
Oshkosh Correctional Institution

Site Designation » 32’ x 12’ CON/SPAN Detention units | Oshkosh, WI
Walmart - West Milwaukee

Site Designation » Ø84” CMP Underground Detention | King, WI
Wisconsin Veterans Home

Design Your Own Detention or Infiltration System
DYODS is our exclusive online design tool to help you calculate the quantity of material
needed for your detention or infiltration system.
You can even compare between CMP, ChamberMaxx and CON/SPAN systems.
Find all the information you need at
www.ContechES.com, including product information,
approvals, brochures, design guides, standard
details and specifications and more.
Quick Links
• LEED information –
www.ContechES.com/leed
• LID Application Guide –
www.ContechES.com/lid
• Professional Development Articles –
www.ContechES.com/pdh
Connect With Us
We're here to make your job easier – and that
includes being able to get in touch with us when you
need to. Search for your local rep at
www.ContechES.com/connectwithcontech
While you’re there, be sure to check out our
upcoming seminar schedule or request an in-house
technical presentation.
Links to Other Stormwater Tools
Check out our design toolbox for all our online tools
and engineering resources, or to start a project at:
www.ContechES.com/designtoolbox
UrbanGreen™ Rainwater Harvesting Runoff
Reduction Calculator
www.ContechES.com/rwh-calculator
Download the Land Value Calculator
www.ContechES.com/l v c
ENGINEERED SOLUTIONS
©2012 Contech Engineered Solutions LLC
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