Last Friday, Saint Patrick’s Day, Washington Suburban Sanitary Commission (WSSC) finally announced completion of repairs to the ruptured 20-inch pressurized sewer main at the Piscataway Wastewater Treatment Plant. The plant has now returned to normal operations.
If you recall, on February 9, 2017 a 52-year-old cast iron sewer main broke, causing approximately 3.35 million gallons of untreated sewage and wastewater to overflow into Piscataway Creek before temporary pumps were set up later the same evening to divert the flow into on-site retention basins.
The Piscataway Plant treats about 24 million gallons of wastewater per day. For about 10 hours almost half of all sewage reaching the plant was flowing to the creek as raw sewage until Washington Suburban Sanitary Commission (WSSC) workers were able to divert the flow into retention basins at the plant. Over that first weekend, WSSC crews and contractors installed temporary pumps and bypass piping at the Piscataway Wastewater Treatment Plant. The bypass diverted the majority of the wastewater flow directly into the plant for treatment. The remainder of the flow continued to be pumped into retention basins on plant grounds.
WSSC and contractors would eventually run three temporary pipes, each 2,000 feet in length, moving wastewater around the broken sewer main to the plant. It took several days to excavate the broken pipe for examination because it was located under a concrete-encased structure that contained approximately 120-feet of high-voltage lines. The electric lines were de-energized and the concrete encasement broken apart to find a pipe that had ruptured its entire length. More than 60 feet of damaged pipe was removed and replaced. WSSC says the total cost of the emergency repairs is approximately $1.3 million.
In addition to the repairs, crews drained the retention basins where overflow sewage had been stored sending the untreated wastewater to the plant for treatment. Crews then analyzed the retention basin soil and determined an additional 1.5 million gallons of wastewater permeated the soil in the retention basins. WSSC has been working with officials from the Maryland Department of the Environment and the Prince George’s County Health Department throughout the repair process to address these environmental impacts.
Remember WSSC’s water and wastewater systems are separate. This overflow did NOT affect WSSC’s drinking water.