Lacombe to Barker Underground Transmission Project

Xcel Energy’s Lacombe to Barker Underground Transmission Project includes the installation of parallel 230-kilovolt underground electrical transmission lines underneath 20^th street from Lacombe Substation west of Chestnut Place to the alley between Blake and Market Streets, and along the alley between 20th Street and the Barker Substation located in the historic district of Lower Downtown and Ballpark neighborhood. Construction of the project in the heart of downtown Denver faced several logistical challenges, including coordination around Colorado Rockies game days and a constricted, urban setting.

The Lacombe to Barker Design and Construction team, comprised of Power Engineers, Brierley Associates, and Michels Corporation, completed the construction of two, 2,100-ft, 14 HDPE pipe duct bundle transmission lines under 20th Street in Lower Downtown Denver by using horizontal direction drilling.

Urban fill was encountered in in all borings along the alignment from the below the pavement to approximately 24 feet below the ground surface. The urban fill consisted of multiples soil types with traces of bricks, asphalt, and rebar. This material was determined to be unstable. Native alluvial soils were encountered below the urban fill on the western half of the project near the South Platte River, ranging in depth from 14 feet to 24 feet below the ground surface. Further below the urban fill and the native soils was bedrock consisting of Denver Formation Claystone.

Brierley Associates worked with Power Engineers to determine feasible trenchless options for a crossing of this length and magnitude, while meeting the ampacity requirements for the cable. The duct bundle required the installation of eight 8-inch ducts and six 4-inch ducts for each installation creating a bundle diameter of approximately 32-inches.

For an HDD option, the conduit bundle strings would be assembled at the entry point. However, due to the close proximity to I-25, the entire 2,100 ft pipe string could not be assembled, and an intermediate fusion point would be required. Additionally, the pipe string layout alternative faced challenges from the need to keep Little Raven Street accessible to I-25 for residents.  This required the pipe bundle to either be trenched below Little Raven Street through a temporary chase or being suspended in the air for the pull-back.

Battling multiple early season snowstorms, the installation of each HDD crossings were successfully completed before the start of the Colorado Rockies 2025 regular season.