The re-construction of Interstate 95 through the City of Philadelphia is currently underway to increase the capacity of the highway, ease congestion, and provide safer travel conditions for motorists. The project is also being used as an opportunity to reconnect parts of the city that were divided when the roadway was originally constructed and to create open public space in an area that historically has had little. A significant challenge with this project has been finding space for stormwater practices in a dense, urbanized environment. Designers and engineers have had to get creative using narrow right-of-way spaces and areas under elevated portions of the roadway. One of the stormwater practices being studied as part of the project is a long linear bioswale nestled between the highway and adjacent properties. At its narrowest, the site is only 20 feet wide yet is 500’ long. To make use of the limited space, gabion mattresses were installed in a 150-foot portion of the bioswale to provide erosion protection and stability on the steep side slopes of the swale. This presentation will examine how the basin has performed over the course of 5 years focusing on the differences between the gabion mattress portion and the more traditional bio-infiltration portions of the site. Historical data measuring ponding levels and drawdown rates will be presented. Benefits and drawbacks of the gabion mattress will be discussed with respect to site access, long term maintenance, and performance.
.jpg "Robert G. Traver, Ph.D.,P.E., D.WRE, F. ASCE photo")