SALEM — It is technically feasible to install high-voltage electrical cables under Salem Harbor, but an underwater project of that scope would cost about $110 million, according to an engineering report released yesterday by National Grid.
The underwater route would be “double the cost” of a proposed land route, the utility said in a recent letter to city councilors.
National Grid released the engineering report in response to a protest by a number of neighbors and businesses that culminated this month with a City Council vote to put a nonbinding ballot question seeking support for the harbor route before voters in November.
Opponents contend the planned land route would disrupt neighborhoods and the central business district, would hurt businesses and could be avoided by using an underwater construction technology that National Grid has used on other projects.
The utility counters that the state’s Energy Facilities Siting Board, which will review the project, would not approve horizontal directional drilling — the technology that would be used to go under Salem Harbor — for this project because it does not meet three key criteria: least cost, least environmental impact and best reliability.
National Grid must replace large underground cables that run from a substation on Fort Avenue next to Salem Harbor Station to another substation on Canal Street. The company has proposed a route that would go down Fort Avenue and Forrester Street, past Salem Common, down Hawthorne Boulevard and Congress Street, through The Point neighborhood and over to Canal Street.
While some past and present city councilors oppose the land route, other elected officials have been more cautious or have pointed out problems with going under the harbor. State Rep. John Keenan, chairman of the Joint Committee on Telecommunications, Utilities and Energy, has noted that it would be much more expensive, a cost that he said would be passed on to rate-payers.
Mayor Kim Driscoll could have blocked the ballot question but decided not to use her veto power. However, it appears she is undecided on the issue and wants to study it more.
“I am very concerned about the proposed cable replacement project and the impact it will have on our residents, businesses, and local economy,” she wrote in an email yesterday.
“With that in mind, we set aside funding as part of this year’s recently adopted budget so that we could undertake a peer review and analysis of the HDD (horizontal directional drilling) option. Now that we have the HDD report from National Grid, we will undertake that review as quickly as possible ...”
The mayor said she will “seek clarification” on “who would bear any additional costs for the HDD option.”
The engineering report commissioned by National Grid did not compare the land and water routes. It focused solely on horizontal directional drilling and raised a number of issues and complications with the proposed path under Salem Harbor.
The report also included some new information.
It stated, for example, that the transmission cables would enter Salem Harbor from the power plant and exit at Palmer Cove baseball field.
Installation of the cables would require construction of one or two temporary platforms in the middle of Salem Harbor, the report stated. That construction would place “permanent restrictions” on use of the area around the platforms due to the shallow burial of cable pipes.
Those restrictions would include dredging, installation of new moorings and anchoring of large ships, the report said.
Risk factors cited in the report include a “likelihood of discovering unfavorable subsurface conditions” in the harbor that could make construction more difficult and longer.
The report also cited potential environmental risks, including “cross-contamination” of soils at the power plant and Palmer Cove, which is located on a capped landfill; and the “inadvertent return of drill mud to the surface at unplanned locations” during fracking, or high-pressure drilling.
The report discussed the potential difficulty of repairing an underwater cable. “A permanent installation of this type presents several long-term maintenance issues,” it stated. “First, should a cable failure occur along the under-harbor portion, it would be difficult to identify and locate the problem area.”
National Grid had pointed out earlier that even if the route went under Salem Harbor, the company would still have to dig up Derby Street to remove existing cables and would still need to install about 1 mile of new transmission lines through The Point and South Salem.
The report concluded that “the project appears to be technically feasible, but with risks, costs, and other considerations as identified and discussed in detail within this document.”
Tom Dalton can be reached at email@example.com.