Wayne Art Center Stormwater Management Techniques

Description

The stormwater management improvements at Wayne Art Center include three rain gardens and a pervious asphalt parking lot with a subsurface storage and infiltration system. The aging stormwater management system constructed in the early 1990s at Wayne Art Center (WAC) had been insufficient at dealing with runoff. The system’s substrate was not effectively draining and overflow mechanisms were not operating according to design. The system was leaking onto the pavement, and 4 or 5 feet of stagnant water always filled the reservoir. New stormwater Best Management Practices (BMPs) were built in conjunction with the conversion of an old Masonic hall into a new art studio along with an expansion of the original WAC building. Instead of demolishing the old stormwater management system and reconstructing a new one, the system was left in place and an investigation of the system took place following the implementation of the new system installation.

The overarching goal of utilizing stormwater BMPs was to achieve zero runoff for most storm events. The stormwater runoff from the impervious surfaces at Wayne Art Center and nearby impervious surfaces overloaded the existing stormwater collection system. WAC’s new stormwater management system reduces flooding, environmental degradation, and pollution. Both flow rates and water volumes are controlled with the help of this system.

The USDA (United States Department of Agriculture) Soil Conservation Service (SCS) Cover Complex Method was utilized to determine the runoff volume for the addition of the new construction. It was determined that 1,351 cubic feet of extra stormwater volume would be generated from the extension based on the 2-year, 24-hour storm. This brings the overall stormwater running off from impervious surfaces to 2,429 cubic feet.

3,423 cubic feet of stormwater storage can be accounted for with the new construction of the recharge bed, and 4,294 cubic feet of water can be infiltrated through the recharge bed’s substrate (calculated conservatively at 1 inch per hour), which equals a total capacity of 7,717 cubic feet. The rain gardens, not included in this calculation for volume capacity, will further reduce flooding during storm events. With these site improvements, the runoff generated by the 2-year storm should be completely captured by the stormwater management system. According to estimates, peak rates for the 2-year storm should be reduced by 73%, while the 100-year storm should have a reduced peak rate of 9%.

Rain water is collected and infiltrated by rain gardens that are filled with native plant species. For a plant list, please click here. For a detailed image of a typical rain garden click here. The drainage area for the system includes the new parking lot, sections of the new WAC extension, half of the converted Masonic hall and the new sidewalks at the front of the building. Roof leaders from the Masonic hall and from the new WAC expansion drain into the rain gardens. Another seepage bed was added at the outlets of the overflow pipes leading from two of the rain gardens. An HDPE riser pipe takes overflow from one of the three rain gardens during a storm event, where it can overflow into the infiltration bed, which is filled with 3 feet of uniformly-graded clean-washed aggregate located beneath the porous pavement parking lot.  40% of the infiltration bed is void space and is able to indefinitely store 1.5 feet of water, or 3,423 cubic feet of stormwater. The infiltration bed itself overflows into a pre-existing pipe 15 inches in diameter that flows below Maplewood Avenue. A new overflow pipe was installed within the existing system to help drain it as well.

The education of the public is a priority since the site serves as a demonstration project in the hope that it will be emulated regionally.

Location

County: Delaware
Watershed: Darby-Cobbs Creek

Wayne Art Center is located at the intersection of Maplewood Avenue and Conestoga Road in Wayne, Pennsylvania. Ithan Creek is the most affected body of water in the vicinity of Wayne Art Center.

Partners

Wayne Art Center
Cahill and Associates, Inc. (engineering firm; consultant)

Cost

PA DEP Growing Greener grant (2002): $63,367

Contact

Courtney E. Marm
Courtney.Marm@ch2m.com
CH2M HILL
1717 Arch Street, Suite 4400
Philadelphia, PA 19103-3916
215-640-9092
www.ch2m.com

Final Site Plan

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