The anticlimactic nor’easter from two weekends ago has raised political storm clouds over the $1.3 billion proposal to improve the region’s aging sewer system.
Even though the storm brought just two inches of rain to Cambridge and Somerville over the weekend of Sept. 25-27, it nevertheless triggered the discharge of more than a million gallons of treated wastewater into the Mystic River. A facility in Somerville operated by the Massachusetts Water Resources Authority (MWRA) released three discharges from two outlets. Two of these were downstream of the Amelia Earhart Dam through an outlet for which the MWRA is solely responsible, while the third discharge occurred upstream of the dam through an outlet for which Somerville and the MWRA are jointly responsible.
The Somerville facility is one of the MWRA’s most frequent overflow sites because of its location upstream of pumping facilities in Everett and Chelsea that regulate wastewater flows toward the Deer Island treatment plant, said Rich Raiche, Somerville’s director of infrastructure and asset management. Deer Island is the primary treatment plant for the MWRA’s regional wastewater system, serving Boston and dozens of surrounding communities.
To keep the plant from becoming overwhelmed during periods of high flow, MWRA officials “deliberately throttle flows at those two locations so that we don’t wash out Deer Island, which would be a much bigger problem,” Raiche said.
For this nor’easter, Cambridge, despite receiving virtually identical rainfall, reported no combined sewer overflows. Lucica Hiller, a senior project manager with Cambridge’s Department of Public Works, said the city’s rain gauges recorded just three-tenths of an inch during the storm’s wettest hour, allowing its sewer system to accommodate the prolonged rainfall. Cambridge’s most recent reported overflow occurred July 29, when 1.57 inches of rain fell. Another occurred July 22, when just 0.57 inches fell, illustrating how even smaller storms can overwhelm the system when rain falls over a shorter period. The July 22 event “was like a quick 30-minute rainstorm, and it was a downpour … so you’re gonna get a CSO because that’s a lot of rain to get in a short amount of time that needs to fit in the pipes,” Hiller said.
The overflows happened as Cambridge, Somerville and the MWRA seek approval for a proposed $1.3 billion plan to reduce combined sewer overflows in the two cities, portions of whose sewer systems date back to the late 1800s. The plan, submitted to state and federal regulators in April, aims to eliminate combined sewer overflows during a typical year of rainfall projected for 2050, accounting for the heavier storms expected to accompany the region’s warming climate.
A global first
Eliminating overflows in an average year is unprecedented globally in its ambition for a combined sewer overflow plan, Raiche said. “This would be the first one to get it down to zero in an average year, and only suffer them in extreme rainfalls,” he said.
The proposal calls for new wastewater storage tanks, separation of stormwater from sewage in portions of the existing sewer network, and upgrades to pipes and other infrastructure to accommodate greater flows. It would not entirely eliminate sewer overflows but aims to limit them to unusually severe storms, even under the wetter climate conditions projected for 2050.
However, it could mean sharply higher taxes for all the MWRA communities, though Cambridge and Somerville would get most of the benefits.
And overflows would still occur. Cambridge, Somerville and the MWRA modeled more extreme storms projected to occur once every five and once every 25 years under future climate conditions. The models showed storms of that magnitude would overwhelm neighborhood sewer systems, causing sewage to back up into homes and flood streets even if the agencies spent more to prevent CSOs. “There’s more and different work that has to happen at the more local level to prevent those,” Raiche said.
At Cambridge City Council Monday councillors will consider a policy order calling on the city to advocate for stronger CSO controls and “virtual CSO elimination by 2050.”
Raiche said the agencies have yet to negotiate a final cost-sharing agreement, but all 43 communities are expected to contribute because they share an interconnected wastewater system.
Big rate hikes expected
For Cambridge residents, the rate hikes would be substantial. Hiller said the city’s financial projections call for annual sewer rate increases of approximately 9% for the first three years, followed by smaller increases in subsequent years. Under the proposed plan, the average annual sewer bill for a single-family household is projected to rise from approximately $1,200 in fiscal 2026 to $3,300 over the next 30 years, an increase of roughly 175%.
Somerville residents face similarly steep increases. Raiche said a typical household currently pays approximately $850 annually for sewer service, a figure projected to rise to $2,600 by 2055, roughly tripling over the next three decades. Cambridge’s projections account for inflation and borrowing costs.
Hiller acknowledged that some residents already struggle to afford their sewer bills, a concern that factored into the city’s decision to support the proposed level of protection. She said those costs have alarmed officials in other MWRA communities, which would help finance the improvements despite receiving little direct benefit from them. “We have started to get comments from other municipalities in the MWRA sewer system that are very worried about the cost of this plan as presented,” she said, warning that some could eventually face costs running into the tens of millions of dollars.
Asked whether those communities would receive any tangible benefits from the improvements in Cambridge and Somerville, Hiller answered simply: “No.”
As to whether they should contribute even so, “I’ll leave that to the politicians and townspeople to decide,” she said.
A harbinger for other systems
The plan’s price tag has also attracted attention from other Massachusetts cities with combined sewer systems. Raiche said officials in Springfield, Haverhill, Lawrence, Lowell, New Bedford and Fall River, none of which belongs to the MWRA system or would contribute to this project, are watching the Cambridge-Somerville proposal because they could eventually face similar requirements from Massachusetts Department of Environmental Protection (MassDEP) to account for future climate conditions. “They’re paying attention to us and saying, ‘Oh boy, the next round is going to be more complicated,'” he said.
The federal Clean Water Act requires Cambridge, Somerville and the MWRA to address sewage overflows. MassDEP determines what level of overflow control the three agencies must achieve to comply with the law and has directed them to account for future climate conditions in their proposed plan.
Raiche said he could not predict whether MassDEP would impose similar climate-related requirements on other Massachusetts cities, but despite the hefty price tag, Cambridge, Somerville and the MWRA must demonstrate progress toward meeting the standards already set for them to avoid potential penalties for noncompliance.
“So far as DEP defines compliance as controlling to a certain level, we have to do that,” Raiche said. “Not to be too cavalier about it, but it is the law.”
The proposal is currently undergoing a public comment period, with the final public hearing scheduled for Wednesday, Oct. 28, from 6 to 8 p.m. at Somerville City Hall. The public comment period closes Friday, Oct. 30.
After the public comment period closes, Cambridge, Somerville and the MWRA must address the feedback and submit a final plan for regulatory review. MassDEP, working with the federal Environmental Protection Agency, will then review the proposal and determine whether to approve it. Under the current regulatory determination, that review period extends through August 2029.
A stronger
Please consider making a financial contribution to maintain, expand and improve Cambridge Day.
We are now a 501(c)(3) nonprofit and all donations are tax deductible.
Please consider a recurring contribution.