Thornton met another roadblock in its years-long effort to install a 72-mile pipe to ferry water from the Cache La Poudre River to its thirsty residents in Denver’s northern suburbs, with the Colorado Court of Appeals on Thursday upholding Larimer County’s denial of a permit to build the project.

The appeals court’s decision means Larimer County’s Feb. 11, 2019, denial of Thornton’s plan to lay a 48-inch-diameter pipe across 27 miles of the county stands. The rest of the $423 million pipe would run through Weld and Adams counties.

Thornton spokesman Todd Barnes said the city was “disappointed” with Thursday’s ruling but said Colorado’s sixth-largest city is “committed to continue seeking solutions outside of the legal process that can meet the needs of our community and those in Larimer County.”

The city could also try to take the case to the Colorado Supreme Court. Barnes said no decisions have been made on next steps.

“We… appreciate that the court agreed with us that the (Larimer County) commissioners abused their discretion by considering certain improper factors,” Barnes said. “Thornton remains committed to bringing the high-quality water we own down to the people in our community.”

While the court of appeals did scold Larimer County on several points in the process, it ultimately concluded that the county did not abuse its discretion in enforcing its land use code to deny the permit.

Residents had denounced the pipeline, saying its construction would negatively impact homes in Larimer County. They urged that the water stay in the Poudre River through Fort Collins before Thornton captures it near Windsor and pipes it south.

Thornton has owned shares in the Poudre River for decades and because of its robust growth over the last decade or so to a city of nearly 150,000 people, it needs to start accessing that water for its future residents.

The city insists it needs a pipe to convey the water because letting it flow through Fort Collins in the Poudre River would degrade its quality.

Thornton sued Larimer County in district court two months after the denial. The Larimer County District Court judge upheld the commissioners’ decision. The city then took the case to the Colorado Court of Appeals.

Thornton says it’s critical that it be able eventually to obtain the water it owns. In 2020, the city began telling developers that it might have to stop issuing building permits if it can’t procure enough water.

The city has a maximum population goal of around 260,000 residents by 2065.