The Vermont Public Utility Commission, in an Oct. 3 notice, said that a public hearing will be held on Oct. 22 in South Burlington, Vt., regarding Green Mountain Power’s (GMP) petition for a certificate of public good authorizing the construction of the new GMP Airport substation on Shamrock Road in South Burlington.
GMP also proposes to reconfigure the existing 3308 34.5-kV transmission circuit; retire, demolish, and remove the existing GMP Airport substation on the VT Air National Guard property; as well as retire and remove the existing Airport Tap, the commission said.
According to GMP’s Aug. 13 petition, the proposed project is needed to improve reliability for Chittenden County to provide greater operating flexibility for feeder backup during planned and emergency outages. The project would also have the ancillary benefit of addressing aging infrastructure at the existing #79 Airport substation, which the company plans to retire as part of the project.
GMP added that the construction of the new Airport substation includes installing three 38-kV vacuum circuit breakers and associated disconnect switches, as well as two 38-kV underground transmission circuit getaways, among other things.
The new GMP Airport substation would include two new 34.5-kV terminals at the GMP Airport substation, which would be inserted into the existing looped 3308 34.5-kV circuit that exists between #19 Essex substation and #17 Lime Kiln substation. GMP also said that three new 60-foot transmission poles would be installed just northeast of the proposed substation location within the existing GMP 34.5-kV right of way (ROW) for the 3307 and 3308 34.5-kV transmission circuits. Two new 38-kV cable and conduit systems would also be installed between the new transmission poles and the substation to facilitate the entry and exit of the 34.5-kV transmission circuits.
Among other things, GMP said that it plans to remove the existing Airport Tap, including the removal of all of the 34.5-kV circuit conductor, removal of four of the seven structures comprising the tap, removal of the three existing 34.5-kV gang-operated loadbreak line disconnect switches, and removal of three of the structures at the origin of the tap.
Three of the existing Airport Tap structures would be retained to continue to support the existing 19G3 12.47-kV circuit conductor, GMP said, adding that the crossarms and insulators that carried the Airport Tap 34.5-kV circuit conductor would be removed on the structures to remain in place, and the 19G3 12.47-kV distribution spacer cable conductor would be raised to increase road clearance, as well as match the profile of the adjacent 19G3 structures.
The anticipated construction schedule for the project is expected to run from March 2019 through October 2019 for the construction of the new Airport substation. GMP added that that schedule anticipates the receipt of a certificate of public good in early February 2019. In addition, the project involves demolition of the existing Airport substation and Airport Tap once VT ANG converts its voltage and following construction of the new Airport substation, GMP noted. The company said that it expects to be able to begin the demolition of the existing Airport substation no later than two years after it puts the new Airport substation into operation.
GMP also said that the estimated cost of the project is about $4.4m.