State approves $1.5-billion Eversource plan to bolster electrical supply in Cambridge, Somerville

The state Energy Facilities Siting Board recently approved plans by Eversource to build a large new underground substation in Kendall Square and 8.5 miles of new high-voltage lines connecting it to other Eversource substations in Brighton and Somerville to deal with growing demand from new construction and electric vehicles - and Vicinity Energy's plans to convert its Kendall Square steam-generating boilers to electric power.

The 229-page ruling in favor of Eversource's "Greater Cambridge Energy Program" rejected MIT's bid to have one proposed conduit moved from Vassar Street to Albany Street, both out of concerns of the impact on its own underground electricity, steam and chilled-water conduits, which run under Vassar, and because of issues involved with roughly two years of construction along that street.

The board concluded that MIT - which actually supports the overall Eversource project - failed to prove that its proposed route would warrant the extra costs and time it would take to design and build.

In its ruling, the board said the project, centered on a large substation to be built 100 feet below 290 Binney St. in Kendall Square, would ease concerns about the power grid in East Cambridge in particular becoming overloaded. The site is the former home of the Blue Garage, whose owner has torn it down to make way for a new mixed-use development - and reached agreement with Eversource to allow construction of a subterranean vault to house the substation.

The record shows that the East Cambridge Substation is at capacity, and load continues to grow in the area which it serves. The record also shows that the Company’s system has exhausted all possible solutions to adequately transfer the load from the East Cambridge Substation. The record also shows that interim measures to mitigate load loss in the absence of a comprehensive solution like the Project, including the addition of a fourth transformer at Putnam Substation and a third transformer at the Somerville Substation, are insufficient.

Eversource estimates it will take five years to build out the new system - which will include a new conduit to be built into the deck of the River Street bridge to cross into Allston/Brighton.

According to the board's decision, Eversource did look at "non-wires alternatives" to expand the capacity of the local grid, including solar power, construction of massive batteries, construction of smaller "district" or distributed energy sources and programs to reduce and better manage demand from end users, but ruled them all out as feasible alternatives; for example, there just isn't enough space in the already densely built Cambridge area to put in enough photovoltaic cells and there is too much demand on the existing power network to fully charge a large-scale battery system to supply power reliably should parts of the existing grid go down.

The plan approved by the state came after complicated routing for the new underground 115-kV transmission lines - which in addition to MIT's concerns, had to take into account everything from the Red Line and placement of existing underground utility conduits to the potential harm to large shade trees from digging large new conduits.

Because the substation would be underground, not all that far from the Charles River, the state also mandated periodic reviews on how to protect it from possible flooding in the increasingly drenching storms would could get as the climate continues to get warmer:

Given the high groundwater levels at the location of the New Substation, as well as the first-of-its-kind underground location of the New Substation, the Siting Board directs the Company to review Cambridge and the state's projections of sea level rise on a periodic basis and submit a report to the Siting Board analyzing the necessity, appropriateness, and cost of implementing additional flood mitigation measures at the New Substation to protect the New Substation from risks due to flooding, every five years following commissioning of the Project

The company will also have to put up signs near exhaust vents from the substation warning them of possible hot temperatures, even though the worst of that would be coming off the top of 35-foot-high stacks:

The record shows that heated air generated within the New Substation vault would be directed to the exhaust stack located in the northwest corner in the plaza above ground. Pedestrians who come within a foot from the exhaust structure could encounter air temperatures of up to 108 degrees Fahrenheit. This impact would diminish rapidly with increased distance from the exhaust structure. For context, the typical temperatures of a dry sauna are between 176 and 220 degrees Fahrenheit, therefore, the Siting Board views the possible maximum temperature of 108 degrees Fahrenheit that could be encountered, which would be unlikely since the vent stacks are 35 feet high, as not likely to cause harm. Nevertheless, to ensure both the well-being and comfort of the general public, we direct the Company to place appropriate and visible signage at the exhaust structure.