The Massachusetts Energy Facilities Siting Board, in a Sept. 8 tentative decision, said that it approves, subject to certain conditions, the petition of NSTAR Electric d/b/a Eversource Energy (NYSE:ES) to build an overhead, 115-kV transmission line on an existing company right of way (ROW) in Walpole, Sharon, Canton, Stoughton, Avon, Randolph, and Holbrook in Massachusetts.
The board said that it approves, subject to certain conditions, Eversource’s petition for a determination that the proposed project is necessary, serves the public convenience, and is consistent with the public interest. Furthermore, the board said that it approves, subject to certain conditions, Eversource’s petition for individual and comprehensive exemptions from the zoning ordinances of Sharon, Walpole, and Holbrook in connection with the proposed transmission facilities.
As noted in the tentative decision, the proposed Walpole to Holbrook Reliability Project consists of a new 14.7-mile, 115-kV overhead transmission line on an existing company ROW between the Walpole substation and the Holbrook substation. The project would use existing transmission structures that currently support a 345-kV line, traveling through Walpole, Sharon, Canton, Stoughton, Avon, Randolph, and Holbrook, the board said.
The project also includes:
- Separating the existing 0.64-mile double-circuit tower (DCT) configuration of two 115-kV transmission lines between the company’s West Walpole and Walpole substations
- Building a new 115-kV switching station on company property in Sharon – the Sharon switching station
- Upgrading existing substations in West Walpole and Holbrook
The board added that the Sharon switching station would consist of:
- Three 115-kV gas-insulated circuit breakers
- A prefabricated control shelter, about 70 feet by 15 feet in area and about 14 feet high
- Related site work to provide lighting, site access, foundations, and underground raceway and grounding systems
The board noted that the project’s estimated cost, based on a planning grade cost estimate (i.e., -25% to +25%), is $34.6m, with a projected in-service date of April 2019.
The board said that the company’s assertion of need for the project is based on ISO New England’s (ISO-NE) “Greater Boston Area Updated Transmission Needs Assessment,” (2015 Needs Assessment), which assessed the ability of the Greater Boston Area transmission system to withstand contingency conditions given projections of peak load, generator availability, and regional power flows.
Eversource’s 115-kV transmission system in the Walpole to Holbrook area is within a braoder transmission area referred to as the “Greater Boston Area,” which generally includes communities north and east of Interstate 495 up to the New Hampshire border, the City of Boston, and suburbs south of Boston, including Medway, Walpole, and Holbrook.
The board added that according to Eversource, the 2015 Needs Assessment showed deficiencies in the Greater Boston Area transmission system when modeled in accordance with NERC, Northeast Power Coordinating Corporation, New England Power Pool, and ISO-NE transmission planning reliability standards.
Eversource stated that the 2015 Needs Assessment identified these capacity and reliability issues within the current 115-kV transmission system between the West Walpole and Holbrook substations based on certain reliability and planning standards and criteria:
- Post N-1 contingency thermal overloads on Line 447-508 in 2018 and 2023
- Post N-1-1 contingency thermal overloads on Lines 447-508, 447-509, and 146-502 in 2018 and 2023
- Post N-1 and N-1-1 contingency consequential load loss in 2018 and 2023
Among other things, the board also said that it finds that the company’s reliability planning criteria, based on ISO-NE’s transmission planning process, are reasonable and that the company used reviewable and appropriate methods for assessing system reliability.
The board said that it approves the company’s petition to build the project using the primary route, subject to certain conditions.
The primary route would extend about 14.7 miles along its existing ROW between the West Walpole and Holbrook substations. Along the first 0.64-mile segment of the route, running east along the ROW between the company’s West Walpole and Walpole substations, the company would separate the existing DCT configuration on 115-kV Lines 146-502 and 447-508 by moving the north 115-kV line conductors to eight new monopole structures, and building a new 115-kV segment. The company would also replace six other structures in essentially their present location within the company’s ROW between the Walpole and Holbrook substations, which varies in width from about 300 to 800 feet, the board added.
The ROW now consists of a lattice-work DCT with two 115-kV circuits, Lines 447-508 and 447-509, on the south side of the ROW, and a lattice-work DCT, occupied only on one side with a 345-kV transmission line (Line 3161/316). The board added that Line 3161, a 345-kV circuit, extends from the West Walpole substation to the Stoughton switching station; Line 316, another 345-kV circuit, extends from the Stoughton switching station to the Holbrook substation; no transmission lines are currently located on the north side of the structures holding Line 3161/316.
The board noted that along the approximately 14 miles of the primary route from the Walpole to Holbrook substations, the company would install new 115-kV line conductors on the north side of the existing DCTs, located along the north side of the company’s approximately 150-foot-wide ROW segment between the Walpole and Holbrook substations, which is cleared to its full width.
The board listed certain conditions, including that the company is to follow all applicable guidelines developed to limit wildlife and resource impacts in vegetation management areas. Also, the company is to adhere to construction best management practices, such as the restoration of disturbed areas after construction, including at the Stoughton switching substation. Additionally, the board said, the company is to offer, on a case-by-case basis, appropriate off-site screening for affected residences in areas of the project where visual impacts may occur, particularly in the vicinity of the West Walpole to Walpole substation DCT separation, the Stoughton switching station, and the Holbrook substation.
According to the Massachusetts Department of Public Utilities’ website, written comments on the tentative decision should be filed with the board by Sept. 15.