Separating Somerville wastewater from stormwater could cost between $550 million to $850 million over 40 to 50 years, with maintenance projects through fiscal year 2030 costing households an estimated $1,200 annually, officials told the City Council last month.
The work has long been underway to keep sewage from flowing into public waters when weather overwhelms system in which pipes for the two kinds of water are connected – a problem worsened by the city being covered by impervious surfaces such as pavement.
The problem is “more than just combined sewer overflows,” director of infrastructure and asset management Rich Raiche said May 22. “The flooding is caused by runoff and hydraulic capacity of the brook.”
State data presented to the council shows an 87 percent reduction in overall water volume of the toxic combination and 93 percent of remaining volume treated since significant work in the late 1980s and early 1990s. Those efforts to decrease the number of days that the mix overflows into local rivers and streams is not enough, said Kristin Anderson, spokesperson for Save the Alewife Brook.
“Alewife Brook floods regularly, sending raw sewage flood water over the banks of the brook and into the [Department of Conservation & Recreation] park, its multiuse path and into the yards and homes of area residents,” Anderson said via email, including images of toilet paper hanging off fencing along the brook banks after an overflow event.
Five thousand people live in the Alewife Brook’s 100-year floodplain, and for the past nine years, the average annual discharges have been double the allowed amount based on a 2008 court case, Anderson said. Advocates such as her group, Green Cambridge and the Alewife Study group want more action now from Somerville, Cambridge and the state’s public water resources and transportation authorities, and for the Department of Environmental Protection to comply with environmental regulations.
Anderson asked the city to find other money to solve the problem, noting that under the previous administration, mayor Joseph Curtatone was able to get a $700,000 loan for assessment and cleanup of brownfields, contaminated properties that cause environmental and public health issues. Thanks to Somerville’s strong bond rating and low interest rates when it borrows money for projects, the city does not use Environmental Protection Agency funding for sewer projects, Raiche said.
“That may change if interest rates continue to increase,” Raiche said, and the city may apply for a state revolving fund program through the Department of Environmental Protection.
Somerville has made progress over the years. Three decades ago, its discharge points were reduced to two from eight, said Raiche, who worked in Cambridge for 15 years on separating the systems there.
City mitigation efforts are now planned for implementation during annual pipeline rehabilitation work that “fixes pipes before they break, but in so doing reduces the amount of groundwater that enters the system,” Raiche said in an email. In coordination with the Massachusetts Water Resources Authority, the provider of Somerville’s water, the city changed its configuration of water flowing into the brook. Both efforts were small in results and “carefully balanced as not to exacerbate the volumes at the Cambridge CSO locations.”
Future transformations to the system will also “be very complicated and will require coordination with MWRA and Cambridge,” because, for example, “much of the infrastructure to separate Somerville sewers would physically be located in Cambridge,” Raiche said in an email. A federally required long-term control plan is in the works with Cambridge and the water authority. “Somerville has been gearing up for this effort since 2016. It’s just a really difficult problem to solve,” Raiche said.
Save the Alewife Brook has demanded elimination of all sewers that combine household and street sewage and wants a safe and fishable brook and green infrastructure that cleans stormwater and reduces flooding. The group said that contaminated floodwaters that have been permitted by the state’s Department of Environmental Protection during certain weather events disrupt ecologies and biodiversity, spread hazardous sewage into parks, yards and homes that in some cases have made residents sick with gastrointestinal illness and will only get worse with climate change, among larger environmental justice concerns.
After a presentation this spring by the local environmental advocacy organization with more than 2,300 signatures of support, the council ordered unanimously that Raiche focus on controlling a combined sewer overflow on borders with Cambridge and Arlington.
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