Meliora Environmental Design, LLC and the Pennsylvania Horticultural Society, funded by the Philadelphia Water Department, designed stormwater improvements at the Waterview Recreation Center to increase the amount of greening on the site, which will help reduce the combined sewer overflow problem in Philadelphia. Specifically, the stormwater design is intended to capture at least the first inch of runoff from the street and sidewalk and to capture roof runoff from the front of the existing building. The combination of BMPs used at the recreation center serves to improve water quality, reduce stormwater runoff volume and act as a demonstration project for the Philadelphia Water Department. It also provides urban green space and helps reduce the urban heat island affects in the area. The project challenges included limited space, sediment laden street runoff, conflicting utilities, disturbed soils, underground structures and limited construction funds.
Porous Concrete Sidewalk
Approximately 300 linear feet of impervious sidewalk area was removed. The existing 12-foot wide sidewalk along McMahon Avenue in front of the recreation center was reduced to a 6-foot wide porous concrete sidewalk with sub-surface aggregate infiltration. The porous concrete has been designed with both deep (minimum of 2 feet) and shallow (6-inch) aggregate infiltration beds.
Tree Trench System
The remainder of the existing sidewalk area (6-feet wide) that was not replaced with porous pavement was converted to stormwater tree trenches planted with street trees and turf grass. The porous concrete and tree trench system was designed to capture and infiltrate street and sidewalk runoff generated from small storm events up to nearly 1.5 inches in magnitude. The trees are regularly and passively irrigated by the captured runoff.
Four modified city-highway grate inlets were installed along the curb of McMahon Avenue to capture and convey runoff from half of the street into the porous concrete/tree trench system. The inlets in will intercept this street runoff and also serve to allow overflow from the system during large storm events; they convey street runoff into the bed and tree trench for storage and infiltration.
Flow-through planter box systems are located on the east and west sides of the main building entrance on McMahon Avenue and have been designed to capture roof runoff for small storms up to 1 inch. Roof leaders in these areas are partially disconnected from the city’s sewer system so that roof runoff is caught by the planter boxes to provide peak rate and volume control, as well as to improve water quality. Concrete splash blocks aid in the drainage of the roof leaders to the surface of the planter box without erosion. The concrete planter boxes are waterproofed to protect the existing building foundation in the vicinity of the splash block. Overflow structures are tied back to the City Sewer System through the existing roof leader connection. The planter boxes are landscaped with native plant species, and an amended soil planting mixture will be installed to support the vegetation.
Watershed: Tacony-Frankford Creek
Michele C. Adams, PE
Meliora Environmental Design, LLC
P.O. Box 942
2114 Kimberton Road
Kimberton, PA 19442