Radian Complex Stormwater Management Techniques


The Radian complex at 3925 Walnut Street is a multi-use facility located in the heart of the University of Pennsylvania’s campus district. Its uses include an 11-story student apartment residence tower constructed over street-level retail space and an open terrace on the second level that is accessible for outdoor activities. The project design incorporates the innovative use of stormwater management BMPs, including a green roof, two underground stormwater detention basins, and a streetscape and front courtyard area made of pervious paving material.

The green roof, located on portions of the terrace level, is irrigated from runoff that is collected and diverted from the conventional roof of the apartment tower. Excess runoff entering the green roof drains to the runoff detention systems installed underground below the complex. The detention systems reduce peak volume contributed to the storm sewer system. The detention system is connected to the city’s storm sewer system for release during non-peak intervals.

The sidewalk streetscape showcases a pervious paving system of interlocking blocks made of porous material that allows runoff to penetrate through the surface and seep through the block into the ground. Runoff also infiltrates into the ground through the spaces between the paver blocks.

In all, the design of the project incorporates a balance between ecology, economics and equity in order to produce a beneficial and aesthetic building in Center City.


County: Philadelphia
Watershed: Schuylkill River


Erdy McHenry Architecture, LLC
Paul H. Yeomans, Inc.
Pennoni Associates, Inc.
Roofscapes, Inc.
The Harman Group


Total for site development: $60 million
Funding partner: University Partners, Atlanta, GA


Andrew Pockl, PE
Pennoni Associates, Inc.
One Drexel Plaza
3001 Market Street, 2nd Floor
Philadelphia, PA 19104
215-222-3000 x3289

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