Boulder’s plan to prevent flooding in the southern part of the city has hit a snag with the state, which won’t approve use of its land for construction of a floodwall. But city staff thinks a compromise is possible, clearing way for a flood protection plan that has been years in the making.

“Our understanding remains that the regulatory issues and legal issues are surmountable,” said Molly Scarbrough, senior project manager, Monday.

City Council is set to receive an update on the project Tuesday. The preliminary design was selected in August, but in notes to officials ahead of Tuesday’s meeting, staff explained that several tradeoffs are needed to make the preferred solution viable. They also included a quick mention that the Colorado Department of Transportation was reluctant to sign off on plans to build a floodwall along U.S. 36, in the state right-of-way.

An agreement was reached between CDOT and the city in the past, Scarbrough said, but turnover at the department changed the situation.

“Staff at the project level have not gone through those efforts yet, the details from a engineering and legal perspective,” she said. “The current status is an unwillingness to work through those details at this time. We’re hoping to have more conversations; we haven’t come to conclusions yet (but) we’re now at a point we felt council needed to be aware that these discussions are happening.”

A spokesperson for CDOT maintained that the state never gave the OK but merely suggested in 2013 that it was “willing to consider allowing the City to construct flood mitigation within our Right of Way,” Jared Fiel said via email.

“They (the city of Boulder) may have taken ‘consider’ as approval. I can’t say much beyond that.”

The issue, Fiel said, is that CDOT and the Federal Highway Administration “cannot allow a flood control structure on Right of Way purchased with federal dollars.”

The section of FHWA guidelines that Fiel cites does not explicitly state that no structures are allowed in the right of way. It does say that FHWA policy is “to avoid support of incompatible flood-plain development” and “to avoid significant (and) longitudinal encroachments, where practicable.”

City staff have interpreted the guidelines differently. Scarbrough said they believe that an existing highway embankment can’t count toward flood mitigation when mapping a floodplain. In other words, if Boulder’s flood plan used U.S. 36 as the floodwall, that wouldn’t fly.

“That’s not what we’re trying to do here,” Scarbrough said. “What we are doing is asking for use of the right of way to take the highways (U.S. 36 and Foothills) out of the floodplain. Ultimately, I can’t imagine that the FHWA would prohibit CDOT from partnering on a project that would take their highway out of the floodplain.”

Doug Hecox, FHWA spokesman, said the group’s policies are meant to generally “keep encroachments or embankments out of floodplains. That can be interpreted in a number of ways.”

They are written to be flexible, he said, because there are so many factors that play into flood protection, some unique to each site. Without knowing more about Boulder’s specific plans, it’s not possible to say if they conform to, or run afoul of, FHWA guidelines.

“We have to talk to the city, look at the pattern of flooding, etc. that might help make for a more informed decision,” Hecox said. “If (what) Boulder is doing help(s) beef up the durability of that embankment, maybe” it would be acceptable.

A representative from FHWA will likely be at Tuesday’s city council meeting, Hecox said, and possibly at Feb. 12 meeting between officials from Boulder and CDOT.

City Council meeting, 6 p.m. Tuesday, Feb. 5, 1777 Broadway

— Shay Castle, boulderbeatnews@gmail.com, @shayshinecastle

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CU South Boulder CDOT city council city of Boulder Colorado Department of Transportation CU South dam detention Federal Highway Administration FHWA flood mitigation flood wall floodplain right-of-way South Boulder Creek U.S. 36