Tri-State Generation and Transmission Association (Tri-State) on May 17 filed with the Colorado Public Utilities Commission an application for a certificate of public convenience and necessity (CPCN) for the Gateway Transmission Project in Weld County.
Tri-State noted that one of its member systems, Poudre Valley Rural Electric Association (PVREA), is experiencing native load growth on its system in northern Weld County. In order to serve that load growth, Tri-State and PVREA are planning to build the new delivery point known as the Gateway Transmission Project, which is needed to facilitate service by Tri-State’s member system to the identified and forecast distribution loads in PVREA’s service territory, Tri-State said.
The project consists of a new 230/115/12.47-kV substation, which is planned to include a 230-kV three-breaker ring bus, expandable to a future breaker-and-half configuration, with one 230/115-kV, 150 MVA transformer, and a four-breaker ring bus on the 115-kV side, also expandable to a breaker-and-half configuration.
Tri-State added that the substation is located adjacent to the existing Platte River Power Authority (PRPA) Boyd-Longs Peak 230-kV transmission line, which would run through the Gateway substation. PRPA would be responsible for sectionalizing its line to accommodate the Gateway substation, and would also build the 230-kV transmission spans that are necessary to connect the substation to the line. Tri-State added that the planned PRPA facilities would be designed, built, and owned by PRPA.
In conjunction with the project, Tri-State also proposes to build certain 115-kV transmission facilities that are necessary to provide a second source for the new Gateway substation and serve the forecast load in the project area. Tri-State added that it plans to build a short, 115-kV transmission line to interconnect with Tri-State’s existing Boyd-Lone Tree 115-kV transmission line.
The project’s 115-kV transmission facilities would be designed and built to meet the audible noise and magnetic field thresholds set by the commission, Tri-State said, noting that it believes that those facilities are properly considered as being built in the ordinary course of business and, therefore, do not require a CPCN.
According to the direct testimony of Grant Lehman, senior manager, Transmission Engineering and Construction, Tri-State, the short, 115-kV transmission interconnection that Tri-State plans to build would create a Boyd-Gateway 115-kV transmission line and a Gateway-Lone Tree 115-kV transmission line.
“We expect to add two new structures in the same right of way as the existing Boyd – Lone Tree 115 kV transmission line in order to allow for a new span of conductor from those structures, across the county road, and onto Tri-State’s new substation steel deadend structures,” Lehman said. “There are no new transmission line structures expected outside of our existing 115 kV transmission line right of way.”
The 115-kV transmission line is planned to utilize self-supporting steel structures, which are expected to typically be around 70 feet to 90 feet in height, Lehman said.
Because there would be two 115-kV transmission tie lines next to each other, separated by a distance of 75 feet, the right of way for the two lines combined would be 175 feet wide, Lehman said, adding that the two new spans of transmission from the two new structures are expected to be less than 500 feet each.
The 115-kV transmission line spans would use a 477 ACSR Hawk conductor, Lehman said.
The project’s estimated cost is $16.2m, Tri-State said in its application. Tri-State also noted that the project is scheduled to begin construction in 2Q19, and all components are expected to be completed in 4Q19. The project is expected to be in service by the end of 2019, Tri-State said.