At a Glance

Philadelphia now has a strategic, streamlined methodology for evaluating potential stormwater retrofit outfalls.

Project Description

The Philadelphia Water Department (PWD) has a well-established history of retrofitting stormwater outfalls in order to deliver better water quality, habitat, and open space to communities. Until recently, the projects pursued have been primarily opportunistic, often driven by committed stakeholders and staff or to address local nuisance and maintenance issues. PWD recognized the need to develop a more proactive and science-based planning process to identify a broader inventory of opportunities for restoration at outfalls. Biohabitats working in partnership with McCormick Taylor helped PWD establish a rapid, repeatable, and effective desktop method to screen stormwater outfalls for retrofit potential before devoting resources to detailed field assessments.

Biohabitats utilized existing GIS data from the City of Philadelphia to locate and evaluate stormwater BMP retrofit locations. Using the GIS data and an understanding of potential design and implementation constraints, Biohabitats developed screening factors and weighting schemes to vet potential retrofit opportunities. The approach was field-verified as an effective method to identify opportunities. The methodology was subsequently used to evaluate nearly 400 outfalls citywide.



Chesapeake/Delaware Bays

Physiographic Province

Piedmont/Inner Coastal Plain


Lower Delaware

Expertise Areas

Climate Change, Community, Conservation, Ecological Restoration, Infrastructure, Urban Ecology, Water


Philadelphia Water Department


Philadelphia, Pennsylvania, United States