Editor’s note: This story was updated Thursday, morning.
Once again, high volume forced Bedford Department of Public Works crews to divert part of the sanitary sewer outflow into the Shawsheen River on Wednesday outside the main sewer pumping station at 299 The Great Road.
But unlike a similar episode on Dec. 18, this time all three pumps were working at capacity.
The diversion is a direct result of about three inches of rain that fell on the town Tuesday night into Wednesday. Simultaneously, the 12 inches of snow the town registered on Sunday were melting. The results are “very high rivers and streams,” said DPW Director David Manugian.
“The high-water level of the Shawsheen River is affecting the ability of our main pumping station to handle the volume,” said Manugian on Wednesday afternoon. “A fraction of the overall flow is being bypassed in order not to overwhelm the system and cause backups and potential property damage upstream.”
Manugian said the overflowing Shawsheen River near the main pumping station has an impact on the sanitary sewer volume, as do inflow and infiltration of rain and snowmelt from groundwater and illegally connected sump pumps.
On Dec. 18, the diversion resulted from reduced capacity since one of the three pumps was disabled for planned maintenance. But on Wednesday, the flow overwhelmed the pumping capacity, the director said. “We are seeing high-volume storms that we need to consider in our future design.”
The problem on Wednesday was discovered around 10 a.m., and within the hour, the DPW had reported discharge of about 5,000 gallons. In an update on Thursday morning, the DPW reported that as of 11:15 a.m., the sanitary sewer overflow was “on-going” and that the discharge estimate climbed to 787,000 gallons released into waterways, including the Shawsheen River (approximately the volume of water in Springs Brook Park). The overflow “likely consists of untreated sewage and waste.”
Manugian noted that a federal stream gauge in the Shawsheen near the DPW building at 314 The Great Road “peaked this morning at about 12.6 feet above the gauge bottom. This is about six inches higher than during the Dec. 18 storm; the typical flow has been a little over nine feet.”
Stream gauge readings are available from https://waterdata.usgs.gov/nwis/uv?site_no=01100571&legacy=1. Stream gauges “are a barometer of change in our storm patterns as well as development patterns,” Manugian noted.
Manugian stressed that “this overflow has no impact on the Town’s drinking water or wells.” The wellfield by the Shawsheen River has been inactive for several years.
The press release reports that potentially affected municipalities include Bedford, Burlington, and Billerica, and potentially affected water bodies include the Shawsheen River. The DPW says, “Avoid contact with these water bodies for 48 hours after the discharge or overflow ceases due to increased health risks from bacteria and other pollutants.”
Besides the sewage diversion, the only problem Manugian noted from the heavy rains was “localized flooding. Railroad Avenue was closed until mid-morning.”
Looking back on the weekend, Manugian said DPW staff members began snow treatment and removal on Saturday evening and continued until after Monday morning’s commute. Private contractors were called in late Saturday and assisted until late Sunday, he said.
“After getting some rest, our staff started sidewalks early Tuesday morning,” Manugian said, adding, “We appreciate the patience of Bedford residents as everyone negotiated the morning commute, buses, trash and recycling pickup, and Christmas tree pickup.”
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