Crews Work to Stanch Sewage Flow into Shawsheen River

Public Works Department crews worked late into the evening on Tuesday to stanch an overflow of untreated waste from the town’s sanitary sewers into the Shawsheen River near the main sewer pumping station at 299 The Great Road.

The problem resulted from the confluence of two events, said DPW Director David Manugian: one of the station’s three pumps was inactive for scheduled maintenance during Monday’s prolonged heavy rain.

“At the peak of this event, we briefly had a flow rate of about four-tenths of a cubic foot per second going into the Shawsheen River. For context, the river was flowing at about 740 cubic feet per second at the stream gauge in Billerica,” he reported. “The river dilutes it significantly.”

Manugian said a DPW staff member noticed a backup on the grounds of the pumping station at about 12:15 p.m., and when the problem was verified, a bypass was set up, diverting the overflow into the river. Meanwhile, the two working pumps continued to work at capacity.

Bedford notified local, state, and federal environmental agencies as well as Billerica and other downstream towns.

Crews had to wait until the flow started to recede before starting to redirect the flow back into the conduits.

“The high flows just have to work their way through the system,” Manugian said, noting that the calculations also factor in anticipated spike in sewer use after dinnertime.

Manugian said Jason Raposa, who heads the DPW Water and Sewer Division, DPW engineer Mike Sprague, and several staff members of the division were on the scene through the afternoon and evening.

Groundwater enters the sanitary sewers through inflow and infiltration – pumps illegally connected from structures, and fissures in the pipes. The town works to minimize these sources, especially since Bedford is charged for all of the outflow entering the metropolitan disposal system.

Although total gallonage is hard to pinpoint, Manugian said, tens of thousands of gallons were diverted into the river.

“For contrast,” Manugian said, “a three-inch rainstorm is about 700 million gallons falling on Bedford.” The town pumps about one billion gallons of sewage into the system per year, which averages to about 2.7 million gallons daily.

Manugian explained that sewer pump maintenance is scheduled months in advance, and December is usually a safe time to shut the equipment down because any heavy precipitation is likely to be snow.

“We periodically have sanitary sewer overflows when flows in the system are unusually high, a force main breaks, or a pump station goes down,” Manugian related. “Since 2014, we’ve had about one a year. In the fall of 2022, we had five on the Middlesex Turnpike force main, and we expedited construction of a new force main in that area. This is the first since then.”

Manugian said everyone should avoid drinking, swimming, boating, or other contact with the river downstream of the overflow for 48 hours after the discharge ceases, “due to increased health risks from bacteria and other pollutants.”

This has no impact on drinking water, he added. The Shawsheen Road wellfields were shut down in 2019 as a precaution and all local water emanates from the metropolitan system.

Editor’s note: The DPW released an update on Wednesday morning. Get more information here.