BY TOM DALTON
---- — SALEM — Although it appears unlikely that National Grid will lay transmission cables under Salem Harbor, the idea has received at least an expression of interest from an unlikely source — the Salem Conservation Commission.
In a March 25 letter to a National Grid consultant, the board commented on the possibility of running the high-voltage electrical cables deep under Salem Harbor using a technology known as horizontal directional drilling.
“Now that National Grid is exploring horizontal directional drilling, the commission would consider a submarine alternative,” ConCom Chairwoman Julia Knisel wrote.
In 2010, the board had strongly opposed another possible underwater technology, the “jet plow method,” which would dig a trench along the ocean floor. The board said it would cause too much damage to the harbor.
Next spring, National Grid expects to begin replacing two high-voltage transmission lines that run from a substation next to the Salem Harbor Station power plant to another substation on Canal Street. The project is expected to take two years.
The plan the utility submits next month to the state Energy Facilities Siting Board will include two recommended land routes: (1) down Derby Street to Canal, the path of the existing cables, and (2) through a Salem Common neighborhood to Hawthorne Boulevard, Congress Street, and through The Point neighborhood to Canal Street.
At a recent meeting with neighborhood groups, several residents raised strong objections to the proposed land routes, which they said would cause major disruptions to businesses and neighbors, and urged the utility to consider going under the harbor.
National Grid said it has rejected drilling under the harbor because it would cost twice as much as a land route, present environmental risks and also raise reliability issues if it ever had to repair the cables underwater. The utility also noted that a tower would have to be erected in the harbor during construction, which would create other problems.
Mayor Kim Driscoll said the city is trying to lessen impacts on residents and will make sure that horizontal directional drilling is “given full and fair consideration” by the state board, but she did not hold out much hope for an underwater route. Given the state board’s “standards and criteria, it seems unlikely they will approve that alternative,” the mayor said.
The ConCom commented on the underwater alternative after National Grid made a recent presentation on the technology to the board.
“Horizontal directional drilling has been used in other areas of Massachusetts to avoid or minimize impacts to sensitive seafloor areas and the shellfish beds by boring below them,” Knisel wrote. “The commission agrees with issues raised by National Grid concerning potential impacts of drill fluids surfacing and boreholes collapsing, as well as from installing a mid-harbor platform” during construction.
“However, the commission is optimistic that National Grid can engineer satisfactory solutions and mitigate temporary environmental impacts.”
National Grid is holding a community open house tomorrow at 5:30 p.m. at the Hawthorne Hotel. There will be a project presentation at 6:30 p.m.
Tom Dalton can be reached at email@example.com.