The influences of urbanization had significant impacts on the Wises Mill watershed. Since the late 1950’s, the contributing watershed has been fully developed. The residential neighborhood’s storm sewers collect stormwater from the 261-acre area that eventually discharges into Wises Mill Run, a tributary of Wissahickon Creek. Over the last 50 years, the accelerated stormwater flows have severely impacted the receiving creek bed. These effects have been significantly exacerbated over the last ten years, as Wises Mill Run has been exposed to several large storm events.
The Philadelphia Water Department (PWD) has identified the existing flow regime is the direct cause of the active erosion of Wises Mill Run, and will construct a two-tiered stormwater treatment wetland at this site to reduce the impacts of erosion. A wetland was selected as a solution because of its ability to reduce storm flows, and thereby reduce the peak flows experienced downstream. The wetland will be created by installing a diversion structure to redirect runoff from the storm sewer to the wetland, which will hold 150,000 cubic feet of storage. A settling pool will offer pretreatment by allowing sediment to settle out of runoff before it enters the second tier. In addition to reducing peak flows, the wetland will provide two to three acres of wet meadow habitat. The wetland would discharge into approximately 1,300 linear feet of restored stream prior to its confluence with the northern branch.
Watershed: Wissahickon Creek
Total: $750,000 ($150,000 design/$600,000 construction)
Philadelphia Water Department
1101 Market Street, 4th Floor
Philadelphia PA 19107