NSTAR Electric d/b/a Eversource Energy (NYSE:ES) on Sept. 30 filed an initial brief with the Massachusetts Energy Facilities Siting Board regarding the company’s proposal to build, operate and maintain new 115-kV line segments and a new 115-kV switching station.
As noted in the initial brief, Eversource in April 2014 filed a petition with the siting board to build, operate and maintain the new overhead transmission line segments – totaling about 14.7 miles – and the new switching station on company-owned property in the Town of Sharon, and to make modifications to two existing substations in the Towns of Walpole and Holbrook.
On the same date, the company filed related petitions with the state Department of Public Utilities (DPU) seeking a determination that the new line is necessary, will serve the public convenience and is consistent with the public interest; as well as individual and comprehensive zoning exemptions from the operation of the zoning bylaws of the Towns of Sharon, Walpole and Holbrook to build the new Sharon switching station and to modify the two existing substations, Holbrook station #478 and West Walpole station #447.
The Section 72 and zoning petitions were referred to the siting board by the DPU and consolidated with the siting board petition. The siting board, the company added, conducted a single adjudicatory proceeding and developed a single evidentiary record for the consolidated petitions.
The company said that the Walpole to Holbrook Reliability Project is part of a comprehensive solution that was identified in an extended transmission study process conducted by ISO New England (ISO-NE) and its Greater Boston Working Group that evaluated the capacity and reliability needs of the transmission system that serves the Greater Boston/Metro West regions of Massachusetts, as well as southern New Hampshire.
The project’s primary purpose is to mitigate potential overloads on Line 146-502 and Lines 447-508/447-509 under certain contingency conditions, and the potential for high consequential load loss under certain contingency conditions. The company also said that there is an immediate need for the proposed transmission system upgrades in order to continue to reliably serve electric customers in the Walpole-Holbrook Area.
The company said that the project would serve the public interest by increasing the reliability and capacity of the regional electric transmission system over the long term, while minimizing environmental impacts and costs.
Further describing the project, the company noted that it would result in three 115-kV circuits between the West Walpole substation and the new Sharon switching station, and three 115-kV circuits between the new Sharon switching station and Holbrook substation.
During construction, best management practices would be implemented to further minimize and mitigate potential impacts to the surrounding area and sensitive resource areas, the company said.
Before construction activities begin, the boundaries of all wetlands would be clearly marked with highly visible plastic flagging tape to minimize the unauthorized encroachment of construction equipment into wetland areas, the company said.
The project would require the construction of only eight new structures between the West Walpole and Walpole substations for the new line because the new circuit would be installed primarily on existing structures, the company said. Primarily, monopole structures would be used, although some three-pole structures would be used near the substations, Eversource said.
Discussing station work, the company said that the proposed Sharon switching station location between the Norwood and Canton taps would provide reliability, operational and maintenance benefits resulting from the segmentation of the three 115-kV circuits into six circuits with the three breaker arrangement. The station property is surrounded by forested land to the north and east, the right of way (ROW) to the south and the Chestnut Tree Cemetery on the other side of Canton Street to the west.
The overall construction cost for the new Walpole to Holbrook Reliability Project, including the new Sharon switching station, is about $34.6m, which is a planning grade estimate with an accuracy of +25%/-25%. The cost of building the new Sharon switching station is about $12.8m, the company added. The company said that it expects that the project cost would be regionalized across all customers served by the distribution companies within the ISO-NE region.
Among other things, the company said that project construction is expected to occur between March 2017 and April 2019.