To understand the reasons behind why PWD outfalls discharge so much trash to the Tookany – Tacony Creek we need to examine PWD’s floatables control program.
PWD’s Floatables Control Program
Philadelphia has used trapped inlets since the late 1800’s to prevent floatables from entering the sewer system. With 100% inlet trapping and regular inlet cleaning, PWD has done a good job controlling floatables from both MS4 and CSO outfalls. PWD also uses vessels in the Delaware and Schuylkill Rivers to collect floating debris.
PWD’s historic approach to floatables control is simply not adequate for current conditions in the Tookany – Tacony Creek. Plastic bags and food wrappers have neutral buoyancy so that they do not necessarily get trapped in the inlet, rather some of this material flows to the sewer where a significant portion of CSO and 100% of MS4 litter is discharged to the creek. In a small creek like the Tookany – Tacony much of it gets caught on rocks and branches, the rest flows downstream to the Delaware River and out to the Bay and Ocean as marine debris.
PWD conducted a 10 year study of outfall netting at T-04. Unfortunately, PWD did not examine the content of the netted debris, rather PWD relied on visual observation. PWD concluded that the majority of the net debris was natural organic material, leaves, and concluded that it was not necessary to upgrade the City’s floatables control program.
The Anacostia Watershed Society conducted a 1 year netting study and found that 10% of their debris was man-made products, like plastic bags and food wrappers. Washington DC and the Maryland Counties are taking aggressive steps to control their stormwater outfall trash discharges because they recognized the importance of controlling plastic bags, food wrappers and other trash that can pass through trapped stormwater inlets.
My work to date has focused on documenting trash in the creek bet and along the banks of the Tookany – Tacony Creek. I can not quantify what portion of PWD’s outfall trash discharge is retained in the creek and what portion passes through the creek to the Delaware River, Bay and Ocean. I suspect that a significant portion of TTF Watershed street litter winds up as marine debris.
A recent UK study on marine debris in the Thames Estuary sheds some light on the fate of street litter. UK scientists placed eel fyke nets at the bottom of the Thames at 7 locations for 3 months. 8,400 pieces of litter were trapped in the 7 nets over a 3 month period from Sept. to December, 2012. Here are 2 quotes from the study authors..
“The waste collected for the study is only a small snapshot of the volume of litter that may exist at the bottom of the Thames.”
“Plastic bags and other large items are unlikely to get caught in the small nets, so the true extent of the problem is still unknown, the researchers said.” ENS, 1/2/14
We have a great deal to learn about green stormwater. My Tookany – Tacony Creek trash surveys demonstrate that PWD discharges large quantities of street litter to the Tookany – Tacony Creek. The Thames study shows that some of this litter will make its way to the Delaware where it will move along the River – Bay bottom and pose a threat to aquatic life.
Philadelphia’s street litter is a significant water pollution problem that needs to be addressed for protection of the small Tookany – Tacony Creek, the Delaware River and Bay as well as the Atlantic Ocean.