In Old Town Fort Collins, just a few blocks from the heart of downtown, crews are moving a massive amount of earth. The multimillion dollar project is the third most expensive in the city鈥檚 history. They鈥檙e installing a new system to control floodwater. If it goes according to plan, most people won鈥檛 even notice it working.
The Oak Street Stormwater project is designed to reroute heavy rains around the homes and businesses of Old Town through a giant underground pipe.
鈥淔looding can be devastating to communities, and it's been devastating in Fort Collins before,鈥� said Heather McDowell, the project鈥檚 manager. 鈥淚t's really easy to forget that when we have a couple of dry years and when we're fighting fires up in the mountains. But flooding happens too鈥�
The city ran a study in 2019 to assess potential damages that would be caused by a major flood in downtown Fort Collins. They found that over 500 buildings would be inundated, causing about $150 million in repair costs. This project, which will cost the city $42 million, aims to avoid that entirely.
McDowell pointed to a storm in July 2023 that brought more than three inches of rain to Old Town. Although relatively minor, it flooded the intersection of College and Mulberry and brought water into downtown businesses.
鈥淭he streets and the piping that are in place now just get overwhelmed very quickly,鈥� she said.
This project on Oak Street aims to make those floods a thing of the past. A series of drains on the uphill side of Old Town would collect water and funnel it into a pipe big enough to stand in. That water would flow East into an existing system of pipes underneath Old Town, traveling just under a mile before emptying into the Cache la Poudre River near the Udall Natural Area.
When completed, the pipe will be able to carry more than 600 cubic feet of water per second. The pipe is effectively able to carry a whole river鈥檚 worth of water. A nearby section of the Poudre River only saw flows higher than 600 cfs during the very peak of summer runoff this year. It only surpassed that mark during 14 days in 2024.
A pipe big enough to carry that much water, and the digging required to get it about 30 feet underground, does not come cheap. Fort Collins imported a giant, earth-moving boring machine from Germany. Using it to carve out space for the pipe costs about $6,000 per foot.
All-in-all, the project鈥檚 $42 million price tag makes it one of the most expensive capital projects ever taken on by Fort Collins. Only Connexion, the community-owned broadband internet service, and the MAX bus rapid transit cost the city more.
Travis Storin, the city鈥檚 Chief Financial Officer, said the project represents 6.5% of the city鈥檚 annual budget. The city鈥檚 stormwater utility, which is largely funded by bill-paying residents, only has a budget of $22 million in 2025.
鈥淭his is kind of multiple years worth of customer bills that ultimately finance a project to this kind of scale,鈥� he said. 鈥淚t's hard to overstate how large the Oak Street project is for a stormwater utility in isolation.鈥�
Storin said this project is a natural progression of the city鈥檚 plan to protect against flooding. In 1997, devastating floods killed five people and caused an estimated $200 million in damages. Heavy rains in 2013 caused widespread flooding around the Front Range, including the largest flood event on the Poudre River in Fort Collins since 1930.
Those events spurred Fort Collins to floodplain management, especially around Spring Creek, and make in an early warning and detection system.
鈥淲ith those big priorities largely behind us,鈥� Storin said, 鈥淲e're moving into maintenance mode on early warning and detection. The downtown outfalls is really the place to go next.鈥�
Fort Collins鈥� latest flood mitigation work comes at a time when cities across the country are dealing with new, elevated risks posed by climate change.
鈥淲e know that storms are getting more frequent,鈥� said Kris Smith, a researcher at the Montana-based think tank Headwaters Economics. 鈥淎 lot more intense rainfall is happening, and because of that, we're just asking a lot of aging infrastructure to do more work.鈥�
Smith said Fort Collins鈥� efforts are a good proactive step. Many times, the kind of rainfall that causes urban flooding and causes relatively small damage to roads and buildings does not qualify for recovery funding from the Federal Emergency Management Authority. Preventing those kinds of damages in the first place makes economic sense in the long run, she said.
Smith also lauded Fort Collins for addressing two problems at one time: flood control and water quality. The Oak Street project includes rain gardens designed to filter pollutants out of stormwater before it flows into the Poudre.
鈥淗istorically, those two goals have not always been addressed at the same time,鈥� she said, 鈥淓ven though they are inherently connected.鈥�
Digging between Mason and Meldrum streets is expected to wrap up near the end of this year. The next two years will bring more closures along Oak Street from Old Town to City Park. The project is to finish in summer 2026.
This story is part of ongoing coverage of the Colorado River, produced by KUNC and supported by the Walton Family Foundation. KUNC is solely responsible for its editorial coverage.
