Philadelphia Water Department | Phildelphia County, PA

This project involved the design, development, and preparation of construction documents for green stormwater infrastructure (GSI) at Wissinoming Park for the City of Philadelphia Water Department (PWD). This project was part of the City’s Clean City, Clean Waters initiative to address the issue of combined sewer flows in Philadelphia over the next 25 years through the management of runoff from more than a third of the impervious surfaces in the combined sewer system using GSI techniques. The investigations took place in three areas of the park:

■ Area A- Swale in the southeastern portion of the park
■ Area B- Baseball Field in northern portion of the park
■ Area C- Soccer Field in southwestern portion of the park

For this assignment, AEG provided geotechnical and infiltration testing services. 15 test borings (10 deep and 5 shallow) were performed for this investigation. The geotechnical investigation included obtaining a drilling subcontractor, obtaining permits, performing soil borings, infiltration testing, and preparation of a geotechnical report.

Double ring infiltration testing was originally planned to be performed in the swale in Area A at a depth of approximately 5 feet below the existing surface. However, upon a field view prior to field activities, the soil ball under a recently uprooted tree in between boring locations A-B3 an A-B2 revealed that mottled soils were present directly beneath the topsoil and gleyed soils (an indication of permanently saturated soil conditions) were present within approximately 1 foot of the surface.

Following completion of the shallow borings, modified borehole percolation testing was performed. Prior to performing the infiltration testing, the bottoms and sides of the borehole were scarified followed by placing gravel at the bottom of the borehole.

In general, the results of this geotechnical evaluation and infiltration testing program indicated that it was not practical for the implementation of conventional infiltration systems in the areas investigated. All work was done in accordance with the Philadelphia Water Department GSI Design Requirements and Guidelines and the Pennsylvania Department of Environmental Protection Best Management Practices Manual.