underground wet ponds for stormwater management in wisconsin

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

a Contech Solution for Stormwater Management

Wet Ponds

Stormwater Solutions from Contech®

2www.ContechES.com/UrbanGreen

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stormwater management

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Table of Contents

Stormwater SolutionsThe Contech fit with WINSLAMM for TSS Removal| 4

Underground Wet PondsModeling Options| 5Wisconsin Project List | 5

Case StudiesSacred Heart Senior Apartments » Saint Francis, WI | 6Redevelopment at Main Street & Pilgrim Road » Menomonee Falls, WI | 8Boucher Automotive Group » Franklin, WI | 10

© 2012 Contech Engineered Solutions LLC

http://www.conteches.com/urbangreen


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.

A Stormwater Solution for Wet Ponds Contech fits WINSLAMM for TSS Removal

with their Underground “Pond”

» Eric Sturm | Project Consultant (608) 215-3937 [email protected]

» Todd Riebau | Project Consultant (608) 576-0109 [email protected]

» Keith Johnson | Sales Engineer (920) 860-0989 [email protected]

Interested in learning more? We’d love to hear from you!


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.

Underground Wet PondsModeling a Contech System in WINSLAMM

Wet Ponds

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.

» 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

We have the experience to prove it. Here are a few examples!

5 www.ContechES.com/UrbanGreen

Case Study for Underground Wet Ponds

Sacred Heart Senior ApartmentsSaint 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

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.



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

Site Designation » 142x91 Underground Storage | Saint Francis, WI


http://www.conteches.com/Site-Management/Document-Management.aspx?Command=Core_Download&EntryId=13288



Redevelopment at Main Street & Pilgrim RoadMenomonee Falls, Wisconsin

Project Team Members:

Owner: Gatlin Development Co. Inc.

Engineer: R.A. Smith National, Inc.

Contractor: D. F. Tomasini Contractors, Inc.

Technical Description: 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.



Redevelopment at Main Street at Pilgrim Road – Walmart


Site Designation » Ø108” CMP Detention | Menomonee Falls, WI


Image © 2012 Google ∫ Map Data © 2012 Google



Boucher Automotive GroupFranklin, Wisconsin

Project Team Members:Owner: Boucher Automotive Group

Engineer: Site Engineering Services

Contractor: D. F. Tomasini Contractors, Inc.

Technical Description: 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.



Boucher Automotive Group


Site Designation » Ø72” Underground Detention | Franklin, WI

Image © 2012 Digital Globe, GeoEye, U.S. Geological Survey ∫ Map Data © 2012 Google



CVS Pharmacy Store


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



Oshkosh Correctional Institution


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



Walmart - West Milwaukee


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





Wisconsin Veterans Home


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

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Links to Other Stormwater ToolsCheck 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 -ca l cu lat or

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