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After decades of planning and years of navigating legal battles, the construction of a much anticipated water pipeline in Northern Colorado is moving forward.

The pipeline, which stretches from northwest of Fort Collins to Thornton, is currently one of the largest construction projects in the state. The project was first envisioned in the 1980s by Thornton city planners, and construction began in the last decade.

"It was a long process," said Todd Barnes, spokesperson for the City of Thornton.

Thornton started buying land and water rights decades ago in preparation for the day when the city would run short of drinking water for its growing population. The planners accurately predicted the future, making their investment in water access at the Poudre River well worth the decades of investment.

However, when the city tried to claim the water they had legally purchased, they were met by legal challenges from Larimer County and organizations seeking to protect the Poudre River in Northern Colorado. The legal battles have been cleared, and the project is once again greenlit.

"The residents of Thornton have been hearing about this for a long time. This is their future water supply," Barnes said.

While Thornton ironed out their legal battles with Larimer County, they began construction of the pipeline in other communities that were more willing to let them start installing the pipe. That included the Town of Windsor, which allowed Thornton to install miles of pipe through its community in 2021 in an effort to make sure future development would not be impacted by the installation of pipe.

"We had some housing developments up north that were going to come in. We put the pipe in knowing we would eventually be able to hook up with those," Barnes said.

For four years, the pipeline through Windsor led to nowhere. Neither end was connected to anything. Now, with its legal challenges clear, Thornton is resuming construction of the pipeline from Windsor down to Thornton. That includes a current project, which is boring under the E-470 tollway.

"This is the Thornton Water Pipeline segment A. Segment A runs from 88th up to 168th," said Bill Renz, project manager for the pipeline.

Renz was standing near a deep hole in the ground that crews had dug. Crews dug deep into the ground in order to then turn and dig horizontally under the interstate to the north. Lined alongside the roadway are pipes that will one day carry water to a water treatment plant.

"This is all welded spiral steel pipe," Renz said.

"The unique challenge here is we are boring a hole under E-470. The bore is about 900 feet long," Barnes said.

CBS News Colorado was there in 2021 when crews completed a similar project, digging under the Poudre River in Windsor to install part of the pipe.

If everything goes to plan, Thornton hopes to have the pipeline delivering water to its community by 2028. The city projects it will provide enough water to carry the city forward for decades to come.

"In this business, you don't get a lot of opportunities to work on what people would consider generational infrastructure," Renz said. "This is a huge deal for the citizens of Thornton and in general for Northern Colorado."

Thornton resumes construction on 70 mile water pipeline from Northern Colorado