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A lake in the middle of a grassy field.
View of Water Storage & Supply Company Reservoir #3 north of Fort Collins on Nov. 8, 2022. (Valerie Mosley, Special to The Colorado Sun)

The city of Thornton took a second shot Monday at finishing a key 70-mile water pipeline by renewing its request for Larimer County to approve the first 10 miles, as more than 10,000 potential homes in Thornton await certainty on finding a water tap. 

Thornton has staged a quiet public relations blitz with Larimer County residents bordering the redrawn pipeline route after the northern Colorado county’s commissioners rejected the first map. Larimer County has the right to review Thornton’s pipeline under state “1041” regulations on land use for big projects. 

Thornton, in Adams County, has for decades reached across county borders to buy up farms and water rights for Cache la Poudre River flows, and now needs to take delivery through a pipeline to keep growing beyond its current population of about 147,000. 

Thornton on Monday filed thousands of supporting pages for a Larimer County 1041 permit. The city rerouted and shortened the Larimer County section of pipeline by miles to address neighbor objections that led to the county rejection in 2019. 

The new route avoids homes and major roads, and runs partially on Thornton-controlled farmland on its way east from a reservoir Thornton has significant control over through its shares in operator Water Supply and Storage Company. The city will need to negotiate right of way with owners of about 20 private properties if the new Larimer County alignment is approved.

The route makes its turn to the south parallel with I-25. Thornton cut the mileage needed in Larimer County by nearly 17 miles, and moved a controversial pumping station 2,000 feet from any residence. 

Seven miles of the pipeline is already finished in Weld County, and Thornton has nearly all the local approvals it needs outside of Larimer County. To smooth the way for a Larimer County permit this time, Thornton sought direct contact with about 400 nearby residents, and 180 came to explanatory forums, Thornton spokesperson Todd Barnes said. 

In the first go-round with Larimer County, Thornton engineers designed the pipeline and then sought feedback, Barnes said. This time, they sought public opinion first, and engineered it afterward. 

“We had robust community feedback. The application not only addresses any temporary construction impacts, but also provides stewardship towards protecting agriculture and natural resources,” Barnes said. 

The dense permit application includes “precise locations” for the pipeline and supporting structures so that neighbors can see potential impacts, Thornton said. Many neighbors considered the old Douglas Road alignment for part of the pipeline to be especially problematic, and Thornton has moved that section. Some of the alignment now runs further south along East County Road 56. 


Thornton has also had multiple conversations with the nonprofit Save the Poudre/Save the Colorado, led by Gary Wockner, which wants to keep as much natural flow as possible in major northern Colorado waterways. Wockner has proposed that Thornton let its water rights flow 14 more miles down the Poudre channel before taking water out by pipeline, to support wildlife habitat and recreation. Save the Colorado also argues many northern Colorado cities have not made all the water conservation efforts they could that would avoid the need for new dams, reservoirs and pipelines. 

Save the Poudre said Thornton was the first to float the river channel option to portions of the pipeline, though the city says that idea was merely an engineering brainstorming session and never a real option.

“It’s still a great idea, and we are still fighting to force them to choose the Poudre River option instead of this zombie pipeline which has risen from the dead,” Wockner said.

Thornton says it is working with conservation groups and cities to guarantee river flows at crucial times, but cannot let all of its water rights run through the river channel and accumulate the PFAS, E. coli and other contaminants along the way. Building a new water treatment plant to clean up the water after running the extra miles in the Poudre channel would cost $800 million, and $44 million a year more to operate than Thornton’s pipeline plan, the city says. 

Over the years, Thornton has bought up the rights to 14,000 acre feet of Poudre River water administered by the Water Supply and Storage Company system, of which Thornton owns just under half. 

It’s unclear how Larimer County’s planning department and commissioners will respond to the renewed permit application even after the extensive changes. The county’s position is that it can’t discuss or negotiate details of a proposal before a permit application is filed, because commissioners sit as a quasi-judicial body when considering their vote. That precludes backroom deals, but also prevents Thornton from getting useful guidance on Larimer County priorities, Thornton officials have said. 

Thornton says pressure to land the Poudre water continues to build, as the city’s other supplies get tapped out by ongoing growth. The city could grow to 240,000 people by 2040, according to economic projections, but thousands of applications for plat approvals for developments are on hold until bigger water supplies are guaranteed. Other Front Range cities and towns have bumped up against similar constraints in recent years. 

“We’ve got quite a few housing projects that are stalled because we can’t guarantee water, and one of those is a pretty significant affordable housing component for Adams County,” Barnes said. 

Update: This story was updated at 3 p.m. Nov. 20, 2023, with an additional quote from a conservation group.

Michael Booth is The Sun’s environment writer, and co-author of The Sun’s weekly climate and health newsletter The Temperature. He and John Ingold host the weekly Sun-Up podcast on The Temperature topics every Thursday. He is co-author with...