If you walk, run, or bike at CU Boulder South, plan around it starting next month. The City of Boulder says the site will close to the public in full beginning the week of Oct. 5, 2026, with construction on the South Boulder Creek flood mitigation project expected to start in early October.
The city points people to city parks and open space trails as alternatives while the site is closed.
Before the closure
Ahead of the full closure, the city says crews will be doing limited preparation work near the warehouse on the site. The closure itself is what changes public access.
What the city plans to build
The project as planned includes an earthen detention dam, a spillway, an outlet tunnel running under U.S. 36, and a groundwater management system. Plans also call for removing the warehouse and the tennis courts on the site, and reestablishing South Loop Drive.
None of it is built yet. The city projects a construction duration of three to five years. According to the city, the completed project would protect roughly 2,300 residents and 260 structures.
Cost, funding, and why it will take longer
The city estimates total cost at $76.5 million, paid from City Council-appropriated stormwater revenues in partnership with the Mile High Flood District. The city says litigation prevents it from bonding for the work, so the project is being funded on a year-to-year cash basis, which lengthens the schedule and raises the cost.
Concrete Express, Incorporated was selected in fall 2025 to lead construction.
The land
A 2021 annexation agreement set the framework for CU to transfer about 155 acres to the city.
Where the details come from
All of the above comes from the city's announcement, which has the full description of the closure and the construction plan: City of Boulder, "City of Boulder to begin construction on South Boulder Creek flood mitigation project." Dates and durations here are the city's expectations and projections, not finished work, and a multiyear build means access at the site could keep changing.