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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.
1)
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.
2)
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.
3)
Inlet Modification – 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.
4)
Planter Boxes - 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.
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