University of Colorado Boulder may have to scrap plans to build student, faculty and staff housing on its undeveloped south campus as a result of Boulder City Council’s pursuit of a reservoir and dam to mitigate flooding from South Boulder Creek.

In a letter sent to Mayor Sam Weaver and Councilwoman Rachel Friend in January, campus leaders formalized their doubts about the housing plan.

The letter came up at a Tuesday city council meeting while city staff and council members discussed the years-long flood mitigation project.

CU Boulder is seeking to annex a 308-acre parcel of land into the city and, in exchange, agreed to give the city 80 acres for flood mitigation. The parcel is directly south of U.S. 36 and Foothills Parkway, and campus leaders plan to develop 129 acres for housing, sports fields and other amenities.

For years, city and campus leaders have gone back and forth on the best way to mitigate the flood risk presented by the creek.

City leaders are currently pursuing an option dubbed Variant I, which would create a reservoir and dam that stretches from the edge of the property to Table Mesa. CU Boulder previously advocated for the option dubbed Variant 2, which would place a floodwall southeast of the south campus.

Variant 2 was nixed by city officials because of concerns over building too close to the U.S. 36 right of way, which is prohibited by the Colorado Department of Transportation, and impacts on open spaces with protected and threatened species.

In a letter dated Jan. 16, CU Boulder Senior Strategic Advisor Frances Draper and Real Estate Services Executive Director Derek Silva pointed out their concerns with the plan.

The city’s current plan will “greatly impact the usability of the property,” Draper and Silva wrote.

The proposed dam is “effectively severing the developable portion of the property from the community.”

Another concern is the proposed reservoir and dam would require so much land that CU would not have the 129 acres it needs to develop the south campus, according to the letter.

If the city continues to pursue Variant 1, Draper and Silva wrote, the best option is for the city to “trade acreage for the flood mitigation project in the public area with the equivalent acreage in the contiguous (open space other) area on the property.”

While they “do not prefer” the Variant 1 proposal, Draper and Silva wrote the university will continue to work with the city to find solutions to flood mitigation and developing the south campus.

Friend, who lives in the area impacted by flooding, said she wasn’t surprised by the university’s letter.

“I’m happy to have it clarified, because I think we need to stop moving the goalposts on this and have everyone on the same page,” she said.

Friend said addressing flood mitigation is urgent because of how many people could be impacted.

“It’s important we move this along as expeditiously and as reasonably as possible and to avoid delays that are unnecessary while still getting the project done right and well,” she said.

Draper said she sees a path forward for the city and university to work together.

“We hope to achieve flood mitigation in a rapid fire fashion,” she said. “We think this ought to get done, we think an annexation can happen. There’s an important thing to achieve here, and that’s flood mitigation, and the important thing we have to achieve is serving the university and the state.”

City staff also gave council members an update on the flood mitigation project’s status at the Tuesday meeting.

Public Works Director Joe Taddeucci told council members the project’s cost is largely dependent on the level of flood protection, with estimated price points for protecting the city from a 100 year flood, 200 year flood or 500 year flood.

The 100-year flood protection is estimated to cost $67 million and protect 2,200 people, the 200-year flood protection is estimated to cost $94 million and would protect 2,800 people and the 500-year flood protection is estimated to cost $110 million and would protect 4,100 people.

The largest expense from a reservoir and dam that protects from a 500-year flood is filling out enough land for CU Boulder to build its facilities, Taddeucci said.