NEPOOL’s Reliability Committee failed to endorse cost overruns on Eversource Energy’s Greater Boston Transmission Project during the committee’s monthly meeting Oct. 20.

The proposal won 60% support, below the 66.7% needed for a recommendation to the PC.

The project’s cost increased by $191 million (33%), primarily because of the underground Wakefield-Woburn, Mystic-Woburn and Sudbury-Hudson lines. Those three lines will cost an additional $147 million, which brings their total to $352 million.

The need to underground the 115-kV Sudbury-Hudson, initially proposed as an overhead line, accounts for an increase to $91 million, which is more than double the original cost of $45.3 million. Eversource was unable to secure property leasing rights from the Massachusetts Bay Transportation Authority (MBTA) for an overhead line. The project has an in-service date of December 2023.

Eversource performed an updated alternative analysis and found that a new 9-mile, 115-kV underground transmission line within an MBTA right of way was the “most cost-effective and constructible alternative.” The two alternatives analyzed — a new 10.3-mile, 115-kV underground transmission line entirely in roadways ($110.4 million), or multiple upgrades to convert a 14.5-mile, 69-kV line to 115 kV, reconductor 11.6 miles of other 115-kV lines and upgrade seven substations ($116.1 million) — had higher costs.

The Wakefield-Woburn and Mystic-Woburn lines increased to a combined $260.6 million from $160.2 million, representing more than half of the total cost increase. Eversource said additional restrictions on the design and construction required a realignment of underground work within roadways to avoid interference with existing utilities. Restrictions on work hours and the number of crews also increased the construction bids, the company said.

The remaining 30 parts of the project saw an additional 12% increase in cost to $411 million from $367 million. However, these transmission cost allocations were previously supported by the RC and approved by ISO-NE.

RC Supports Proposed Revision to ISO-NE/NYISO Coordination Agreement

The RC voted in support of the RTO’s proposed revisions to its Coordination Agreement (CA) with NYISO to eliminate the need to make a FERC filing when the grid operators update their description of shared interconnection facilities.

The grid operators share interconnections at NY/NE Northern AC Interconnection (comprising the PV-20, K7, K6, E205W, 393, 690/FV and 398 interties), the Northport-Norwalk Harbor Cable and the Cross-Sound Cable Interconnection (CSC).

ISO-NE and NYISO will update the detailed list of interconnection facilities on their respective websites rather than maintaining it in Schedule A of the CA, which requires a FERC filing any time changes are made to it. The addition or removal of an interconnection would still go through the grid operators’ respective stakeholder processes and filed with FERC.

ISO-NE and NYISO have agreed to add the “+/-” notation to the CSC Intertie, which is in the list of interconnections within the list of interconnection facilities that will be posted on both websites. ISO-NE will use “its best efforts” to notify the RC within one week following the posting of any revision to the listing of interconnections. If an RC member identifies and reports a perceived error, the RTO will contact NYISO and discuss the concern. The posting will be modified if they agree a change is warranted. ISO-NE will notify the RC member and explain why the change is not justified as well. Entities can also subscribe to the ISO-NE webpage to receive immediate notices of the revision of posted documents.

The Participants Committee will vote on the CA revisions at its Nov. 5 meeting. ISO-NE and NYISO expect to file the revised CA by the end of the year with an effective date in early 2021.

ICR and Related Values for ARAs Recommended by Vote

The RC voted to recommend that the PC support ISO-NE’s proposed installed capacity requirement (ICR) and related values for Forward Capacity Auction 12’s three annual reconfiguration auctions (ARAs) to be conducted in 2021.

The committee approved net ICRs of 32,925 MW for 2021/22 (ARA 3), 32,765 MW for 2022/23 (ARA 2) and 32,980 MW for 2023/24 (ARA 1). The committee also approved a 958-MW value for the Hydro-Québec interconnection capability credit for ARA 3, with the amount rising to 969 MW for ARA 2 and down to 941 MW for ARA 1.

The PC will vote on the ICR and related values on Nov. 5, with a FERC filing expected by Nov. 30.