BY MARGARET SHAKESPEARE
A sophisticated stormwater system elevates Philadelphia?s Girard Avenue interchange.
FROM THE NOVEMBER 2017 ISSUE OF LANDSCAPE ARCHITECTURE MAGAZINE.
Around the world, cities are demolishing, burying, or capping their elevated freeways, but an interstate in Philadelphia provides a possible alternative?one in which the highway stays up but connectivity, open space, and water quality are still prized. In redesigning three miles of Interstate 95 north of Center City Philadelphia, the Pennsylvania Department of Transportation planned 27 acres of park and open space, and the first phase of the $1 billion project, due for completion by 2027, incorporates examples of green infrastructure. According to AECOM, the prime consultant on the project, landscape design and green infrastructure accounted for between 5 and 7 percent of the first phase?s total budget. At the Girard Avenue Interchange, I-95 runs parallel to the Delaware River two blocks away. Rather than whisking stormwater runoff directly into the river, overtaxing an already burdened municipal system, or funneling a deluge into a rock pit, AECOM and other experts devised a treatment scheme of basins, weirs, bioswales, and rain gardens. Ten planted acres can capture the first inch of runoff from about 50 acres of road surface. ?The water design actually improves the water table,? says Christian Lynn, ASLA, a landscape architect at AECOM.
Water resource engineer Edwina Lam, also with AECOM, explains, ...