By Anne-Marie Lambert
All images and graphics courtesy of the Town of Belmont, prepared for the town by Stantec Consulting Services Inc.
A home in Belmont with four occupants sends about 210 gallons a day of wastewater into the town sewer system.1 When an underground sanitary sewer pipe collapses in a neighborhood where the storm drain is located below the sewer in the same underground trench, the sewage leaks into the storm drain and then into our rivers and ponds. This happened on Homer Road, a small street off Hastings Road. The sewer pipe and storm drain serve three homes upstream of a recently detected collapse.
It is quite common for sewer pipes to be above stormwater drains in Belmont. Stormwater drains were originally installed to capture rain from streets, and were only later used to capture runoff from homes. In a number of locations, the stormwater drains are purposely placed relatively low and with open joints so that rising groundwater can be directed towards streams and ponds, reducing flooding to neighborhoods.
The sewer pipe is located above the storm drain in this repair under Homer Road.
Glenn Clancy, Belmont’s director of Community Development, does not know how long the sewer pipe under the intersection of Homer Road at Brettwood Road had been collapsed before recent CCTV camera footage confirmed the collapse was the cause of the E. coli detected downstream. His staff checked for recent “Dig Safe” markings on nearby utilities like gas and electric to see if they would reveal a possible cause but mainly focused on addressing the $8,500 repair. The repair was completed June 13 by local contractor F.E. French, in time to be included in the town’s July 3 compliance report to the US Environmental Protection Agency (EPA). The town is working under a federal consent order to reduce the pollution it sends into Boston Harbor. Thanks to this repair, an estimated 630 gallons per day of sewage are now flowing to the treatment plant at Deer Island in Boston Harbor rather than through the storm drain system into Wellington Brook.
Similar to the Winn’s Brook story reported in March (“Sewer Leaks Mean Detective Work,” BCF Newsletter, March/April 2018), the detective work which led to the identification of this underground leak started with water-quality measurements at the outlets to Wellington Brook at the bottom of Belmont Hill, where contamination has been measured for over a decade. Starting in 2017, this was followed by measurements in each major stormwater catchment area in town.
Wellington Brook and Winn’s Brook outfall drainage areas, showing Areas 8-4 and 8-5.
The land and drains sending stormwater into Wellington Brook are divided into eight distinct “sub-catchment areas” (see map above). Measurements taken last year at a point near Pearson Road where stormwater in a Wellington Brook sub-catchment area on the west side of upper Common Street (area 8-5) flows into the sub-catchment area that includes the stone bridge by Belmont Center (area 8-4) showed extraordinary levels of contamination. In this area, the sewer and storm drain pipes often take quite different routes downhill—in some blocks they even tilt in opposite directions. Of the upstream locations in area 8-5 that engineers checked next, the drain under the intersection of Brettwood and Pierce was one of the worst.
The next step after testing stormwater in the drains is to do selective door-to-door dye testing of homes in the upstream neighborhood: this involves depositing dye into basement plumbing then monitoring at a manhole to see if the dye shows up in the downstream storm drain system, indicating there is seepage between the sewer system and the storm drain system. Using this method, engineers were able to narrow the problem down to the intersection of Homer Road and Brettwood Road. Stantec engineers then opened a nearby manhole cover and used special CCTV camera equipment to inspect the drain and confirm the likely culprit: sewer and stormwater damage in the same location.
“Mystery pipes,” such as this PVC pipe, top right, found under the intersection of Orchard and Common Streets, can cause expensive additional work when the town must redirect them from the stormwater drainage system to the sewer system.
Because the job was under $10,000, Clancy was able to solicit three contractors without a formal bidding process and have the repair completed within the 60 days required by the EPA. In the past, this type of problem might have taken years to find and fix through the town’s Pavement Management Program (PMP). As it turns out, Homer Road happened to be on the list of roads to assess under PMP in 2018 anyway. However, due to the time required to analyze a new road survey earlier this year, Clancy estimates that the earliest this Homer Road repair would have been found and completed under the PMP would have been October. As a result of the town’s detective work, four months’ worth of wastewater from three households are now flowing to Deer Island instead of Wellington Brook.
Lining Laterals
Sometimes dye testing reveals a problem with the lateral pipes connecting a home to the sewer under the street. When a lateral is cracked but not collapsed, the problem can be fixed by working from the manhole to reline the lateral, without digging up someone’s yard and the street. The past year of detective work has identified at least four laterals in need of relining.
In anticipation of the need for this type of repair work, this summer the town solicited bids and opened a contract with National Water Main for $164,700 to cover relining work based on the length and diameter and connection type associated with each type of repair. This is a new type of contract for the town. The goal is to make it easier for the town to meet the EPA’s 60-day turnaround time once the need is confirmed.
Mystery Pipes
In the process of inspecting town drains, CCTV cameras revealed a third type of problem: mystery pipes feeding into the main drains but not recorded on town maps. These represent illicit connections from the sewer system to the stormwater system. From its opening under the intersection of Orchard and Common Streets, Stantec engineers sent a small “push camera” 76 feet up two 4-inch mystery pipes but could not find the source. It remains a mystery when this happened and whether this was a simple mistake, or a conscious (and successful) attempt to avoid a more expensive solution to diverting wastewater from a renovation or development, or simply an attempt to avoid permitting fees, which have been in place for about 10 years.
Regardless of the motivation, in one case, it is relatively straightforward for the town to use taxpayer money to redirect the mystery pipe from the stormwater drainage system to the sewer system. Here, too, as long as the job is under $10,000, state law allows the town to solicit quotes from three contractors and get it repaired in relatively short order. In the other case, the mystery pipe is lower than the sewer main, so a pump would be required to redirect its contents. Town engineers are debating what action to take.
Next Chapter
Clancy is pleased with progress so far, especially with the fact that the town is already making early progress on meeting a November deadline to measure the remaining Winn’s Brook catchment areas, e.g., those draining into Spy Pond. He and his staff are still deciding whether to go ahead and line all the laterals in similar condition in a neighborhood where a problem has been found. He may also consider testing for downstream pollution when other utility work risks damaging sewer or stormwater drains.
While it’s great to see concrete actions to reduce water pollution, I find it discouraging that a sewer collapse was found so close to the periphery of the drainage system and that sewers can be vulnerable to collapse from nearby utility work. Clancy doesn’t agree: he was expecting to find even more problems and has confidence the town can meet the EPA requirement to clean up all the problems within five years. I hope he’s right.
Anne-Marie Lambert is a director of the Belmont Citizens Forum.
Footnote
1 This estimate appears in a July 31 “Report on Compliance” by the town’s engineering contractor Stantec and is based on the most recent data available from the Massachusetts Water Resources Association. The MWRA bills the town for delivering clean water and for treating wastewater coming from Belmont at the Deer Island treatment plant in Boston Harbor. Part of the bill is based on the volume of wastewater per household. MWRA then pumps the treated water into a nine-mile conduit out to the middle of Massachusetts Bay.
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