Gilmore and Associates converted an 11.5-acre Kennett Square farm into the campus of Chatham Financial’s company headquarters. To prevent impacts to a nearby tributary of the East Branch Red Clay Creek, stormwater BMPs were constructed to address site runoff.
Stormwater management techniques were completed in 2006, preceding the completion of all phases of development. A pond on site was modified into a wet-pond/retention basin. Runoff is directed into the pond’s forebays, which pre-treat runoff by slowing its speed and providing some settling of pollutants prior to its entry into a wet-pond/retention basin for further sediment settling. By capturing, storing, and infiltrating runoff, the wet-pond also helps reduce the peak volume of runoff entering the stream after a storm. This pond also provides storage capacity for floods. The pond includes an outlet structure and spillway for the controlled release of captured runoff. An earthen berm constructed around the pond’s inner edge promotes the growth of aquatic vegetation for filtering pollutants and slowing the speed of runoff. A second small runoff detention facility was implemented on the eastern side of the site.
Runoff flowing off the parking lot enters one of the seven infiltration trenches constructed around its perimeter. An underground infiltration gallery provides storage of runoff beneath the parking lot.
A meadow was installed and site landscaping incorporated the use of native species, providing bioremediation processes and deep root systems that absorb more water than regular sod.
Watershed: Red & White Clay Creek
Christopher D. Burkett, PE, RLA
Project Civil Engineer
Gilmore & Associates, Inc.
221-B Gale Lane
Kennett Square, PA 19348