The City of Garland, Texas on July 21 filed with the Public Utility Commission (PUC) of Texas an application to amend a certificate of convenience and necessity for the proposed Dent Road to Shelby 138-kV Transmission Line in Hunt County, Texas.
According to the application, Garland is proposing to build the new single-circuit line on primarily double-circuit capable steel and/or concrete single-pole structures. The line would extend from the expansion of the Dent Road substation, generally to the northwest, until it reaches the existing Texas Municipal Power Agency (TMPA) Shelby substation, the application noted.
Alternative structure types, such as H-frames, may be used due to engineering constraints, which can include Federal Aviation Administration height limitations.
The typical structure for the project would range from 95 feet to 115 feet in height, but the height may vary depending on the clearance requirements at a particular location, due to the terrain, span lengths, and overhead obstructions, the application added.
The Dent Road Substation Expansion is a new 138-kV station to be built by Garland adjacent to, and south of, the existing Greenville Electric Utility System (GEUS) 69-kV Dent Road substation, the application noted, adding that the station would be located in Hunt County.
The proposed Dent Road to Shelby line project, which is needed to ensure system reliability in the Greenville, Texas area, is one component of the Greenville Area Project evaluated and accepted by ERCOT by letter dated Feb. 15, 2016, to address system reliability issues in the Greenville area, the application noted.
The city of Greenville is located 45 miles northeast of Dallas and served by the GEUS distribution system, the application said, adding that the primary transmission voltage for the GEUS system is 69 kV; there are two TMPA 138-kV transmission lines that interconnect the GEUS system to the ERCOT grid from the west and south.
Due to the age of local generation, there is a concern for the reliability of the Greenville area, the application said. In addition, studies have shown that under N-1 conditions, the Greenville area has significant voltage dips with the loss of one of the 138-kV ties.
ERCOT’s recommendations included:
- 1) Expanding the existing Dent Road 69-kV substation to allow a new 138-kV ring bus configuration and adding a 138/69-kV 150MVA autotransformer
- 2) Expanding the Shelby substation to allow an additional 138-kV transmission line
- 3) Expanding the Wieland substation to allow an additional 138-kV transmission line
- 4) Building a new 138-kV line interconnecting the Shelby substation to the expanded Dent Road substation – about 3.5 miles
- 5) Building a new 138-kV line between the expanded Dent Road substation and Wieland substation – about five miles
For its role in the Greenville Area Project, Garland would build components 1, 2, and 4 at the request of GEUS (owner of the existing Dent Road substation) and TMPA (owner of the existing Shelby substation). Garland would build the associated Dent Road 138-kV Expansion; the 138-kV breaker position at the Shelby substation; and the new Dent Road Expansion to Shelby 138-kV line, the application added.
The number of miles of right of way (ROW) for all 17 alternative routes for the proposed Dent Road to Shelby line ranges from about 4.2 miles for “Route J,” to about eight miles for “Route A,” the application said. Initially, the line would be built with one circuit installed and the number of miles of circuit would be the same as the number of miles of ROW, the application noted, adding that when the second circuit is installed, the number of miles of new transmission line circuit for the 17 alternative routes would range from about 8.4 miles for Route J to about 15.9 miles for Route A.
None of the ROW has been acquired.
The application also noted that the area traversed by the line is located in the Blackland Prairies Physiographic Province of Texas, which represents the innermost subdivision of the Gulf Coastal Plains and is characterized by gently rolling to level terrain with black clay soils weathered from chalks and marls. About 80% of the study area is located within the City of Greenville’s corporate boundary, which is the largest city in Hunt County.
Most of the study area is currently rural, and devoted to agricultural uses. The application also noted that while residential and commercial development occurs throughout the study area, it is most heavily concentrated in the eastern portion, particularly in the vicinity of IH-30 and SH 34. Furthermore, the landscape has experienced a high degree of alteration due to agricultural uses, residential and commercial development, transportation corridors, as well as existing electrical transmission and distribution facilities, according to the application.
Burns & McDonnell Engineering Company, which prepared an environmental assessment and alternative routing analysis (EA), recommended Route J as the route that best addresses certain requirements from an environmental and land use perspective. The application added that Garland also determined that Route J provides the best balance of routing characteristics and best addresses certain requirements.
There are six habitable structures that are within 300 feet of the centerline of Route J, the application noted, adding that five alternative routes, including Route J, are located within 1,000 feet of one park or recreational area, while nine alternative routes, including Route J, each has one cultural resource site within 1,000 feet of its centerline.
According to the filing, Route J has an estimated ROW length of 4.19 miles, and an estimated transmission cost of about $6.3m.
Among other things, the application noted that the estimated schedule calls for ROW and land acquisition to begin in July 2018, and be completed in May 2019; engineering and design would begin in July 2018, and be completed in March 2019; material and equipment procurement would begin in November 2018, and be completed in May 2019; and construction of facilities would begin in May 2019, and be completed in October 2019, which is when the facilities would be energized.