A massive pollution cleanup effort in the Potomac River has hit a snag.
DC utility agency DC Water has been working to mitigate the damage caused by a January 19 sewage pipe burst. A section of sewer line collapsed along Clara Barton Parkway at the 495 interchange and C&O Canal National Historical Park. It caused an estimated 40 million gallons of wastewater a day to enter the Potomac.
Large Rock Dam Discovered
On February 5, DC Water posted an update that it had discovered a large rock dam “stretching approximately 30 feet downstream of the original failure.” It estimates that removing the dam will extend the cleanup and repair timeline by four to six weeks. The extra time will be needed to mobilize the heavy equipment and manual labor needed to remove the large boulders inside the sewer line.
DC Water says the existing bypass system it put in place “has mostly contained overflows,” but “more pumps are needed to further reduce the remaining flow getting through the pipe. A bulkhead will then be installed upstream of the failure to block the pipe and limit the wastewater reaching the collapse site.”
The large rocks were likely excavated during original sewage line construction in the 1960s and used as backfill, DC Water said. When the failure occurred, “this material collapsed into the interceptor drawn in by the force of wastewater flow, eventually accumulating and creating this rock dam. Additional rock and soil entered the pipe as surrounding material eroded into the sinkhole created by the collapse.”
Environmental Impact
As DC Water works to repair the pipe, local environmental groups have been sounding the alarm over potential harm to humans and wildlife. In a January 27 news release, Potomac Riverkeeper Network (PRKN), a nonprofit that works to protect the Potomac River’s water quality, said its sampling data showed the spill’s effects are “far worse impact than originally contemplated.”
PRKN sampled water at Fletchers Cove near Georgetown, which is across the river from Potomac Overlook Regional Park in Arlington. “These measurements of E. coli bacteria show contamination which is nearly 12,000 times what authorities limit for human contact,” said Betsy Nicholas, PRKN president. “And so far, almost 300 million gallons have entered the Potomac River. The long term impact cannot be overstated.”
DC Water says it continues to work with federal, state, and local regulators to evaluate the spill’s environmental impact. The agency says it is also performing water quality sampling at several locations.
On February 6, the agency posted its latest water quality sampling results. “Since February 1, E. coli concentrations at all downstream sampling locations have remained within the U.S. Environmental Protection Agency’s acceptable range for primary contact recreational activities, apart from a single day at Fletcher’s Boathouse,” DC Water reported.
DC Water said that sampling within the drainage channel where the overflow occurred continues to show elevated E. coli levels. However, it said that this is “not unexpected, given intermittent residual discharges and snowmelt carrying remaining wastewater from the creek bed into the channel. Concentrations in this area are expected to fluctuate until residual material is fully flushed and baseline conditions are restored.”
Feature image, josephgruber/stock.adobe.com
