On Tuesday, March 5, John Lisle, vice president of marketing and communications at DC Water, said Fairfax County's Feb. 27 presentation at the Great Falls Community meeting was comparable to DC Water's previous community meetings held the week before.

“We had a hydrogeologist present his findings from his assessment, and they were very similar to what Mr. Herrington presented [on Feb. 27].  The conclusion was the same. There was no evidence that the pipe's failure had compromised the water quality of those homes.” 

Lisle clarified that the broken pipe was part of a larger Manhole 31 Project to upgrade and rehabilitate the Potomac Interceptor (PI).

Lisle explained that a sinkhole formed when dirt entered a pipe, potentially blocking the flow and causing it to expand into a sinkhole. According to Lisle, DC Water conducted all water quality testing at the homes until the transition to Fairfax County last week. DC Water informed residents of positive coliform and E. coli test results in their water supply, and Fairfax County provided guidance on boiling water as a precaution. 

According to DC Water, it is rehabilitating 140 feet of the 54-inch diameter reinforced concrete pipe downstream from Manhole 31, replacing  200 feet of 54-inch diameter reinforced concrete pipe immediately upstream of Manhole 31, replacing Manhole 31 and demolishing the old existing piping as part of the Manhole 31 Project, DC Water. “The old manhole is very close to the new one, Lisle added.

The Potomac Interceptor (PI) is an essential part of DC Water's sewer system that serves Virginia's Loudoun and Fairfax counties and Montgomery County, Maryland. These locations send sewage to the Potomac Pumping Station in DC via the Potomac Interceptor. The Blue Plains Advanced Wastewater Treatment Plant treats discharge from the Pumping Station. DC Water is assessing the PI and has several Capital Improvement Projects to rehabilitate defective segments.