Thornton restarts construction on disputed 70-mile northern Colo. water pipeline
After decades of planning and years of legal disputes, the City of Thornton has resumed construction on a 70-mile water pipeline designed to secure future drinking water supplies for its growing population.

According to CBS News, the project, one of the largest active infrastructure undertakings in Colorado, was first proposed in the 1980s when city officials began acquiring land and water rights from the Poudre River. Those early investments were intended to safeguard against long-term water shortages—a prediction that has proven accurate as the city continues to expand.
Legal challenges from Larimer County and environmental groups stalled the project for years, delaying Thornton’s ability to access the water it had purchased, CBS News reported. With those disputes now resolved, the city is moving forward on construction segments that will ultimately connect the Poudre River to a new water treatment facility in Thornton.
Crews previously installed several miles of pipe through the Town of Windsor in 2021 to accommodate future housing development. For years, that section of pipeline remained unused while legal issues were addressed. With approvals in place, Thornton has restarted construction south of Windsor, including a current effort to bore beneath the E-470 tollway.
Project leaders said the new pipeline uses welded spiral steel pipe and includes complex underground boring operations—such as a 900-foot horizontal dig under the interstate—to minimize surface disruption.
Thornton expects the pipeline to be operational by 2028. Once complete, the system will provide a reliable water supply for decades. City officials describe the project as “generational infrastructure” that will have lasting benefits for residents across Northern Colorado.
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