Longer, smaller or more expensive: For Boulder’s flood work to continue, tradeoffs necessary

Photo by jonathan Ford on Unsplash

Boulder City Council’s preferred flood protection measure needs a little cajoling to be workable, according to a staff report prepared ahead of Tuesday’s meeting.

In its current iteration, the plans will ensnare land that the property owner —  the University of Colorado — hopes to develop and land that the city hopes to preserve as open space. The cost will also be double of the plan presented and approved by council in August.

Shrinking a detention pond would avoid those issues but reduce capacity and therefore protection from larger storm events. Adding to the uncertainty is the state’s refusal to sign off on the project, despite providing earlier approval, placing a critical piece of property in limbo.

The path to flood protection and annexation has been years in the making. CU will add its 308-acre parcel into Boulder in exchange for allowing the city to use some of the land for a flood wall and stormwater detentions. Design options were explored last year; council chose the Variant 1 concept in August, with a request for additional water storage that required more excavation than Variant 1 initially called for.

In order to meet the desired storage capacity in the space allotted for it, the detention area will have to be dug deep and flat at the bottom, staff said, resulting in standing water. A slight slope could be added to facilitate drainage, but doing so will cause the detention area to encroach on land intended for other purposes: approximately 5 acres of property CU wants to use for athletic fields would need to be excavated, along with 17 acres that the city hopes to preserve and enhance as open space.

Officials at have indicated that the university expects to get the full 129 acres for development set aside during the land use discussion, including 30 acres for athletic fields. Council’s October discussion included ways the city could swap other land to get CU its acreage, something staff noted in its memo.

“Although the improved drainage in this concept avoids large areas of standing water allowing for easier maintenance and improved ecosystem functions, the detention area would not provide adequate drainage to support turf for recreation or sports fields,” they wrote. “Based on CU Boulder’s previously stated interests, if the detention area was not viable for recreation uses, they would expect to reserve other areas of the site for that purpose, likely in areas that the city is seeking to acquire as Open Space.”

Frances Draper, CU’s vice chancellor for strategic relations and communications, said there have not been further discussions with the city about potential land swaps, but that the university is flexible — so long as it gets the same total amount of buildable land.

“We have structured the application so that Council may move the lines for the flood project as they determine the best course,” Draper said via email, “and then it would be up to them to determine which 129 acres we could develop, with our agreement.”

The revised excavation plan (which includes the gentle slope) also costs nearly twice what the original Variant 1 concept would: an estimated $65-75 million. Boulder’s capital improvement program budget anticipates a $31 million project, paid for in higher stormwater and flood management fees to cover debt funding on a 20-year bond.

Each additional $10 million needed for the South Boulder Creek work will add roughly $19 per household annually for two decades to those rate increases. For a $65 million project, that pencils out to roughly $1,330 per home over 20 years. For a $75 million project, it would be $1,710.

The detention area could be made to fit only on the land originally set aside for it, zoned Parks Urban Other, but it would reduce protection as well. The project as devised would protect from a 500-year storm event, which has a .2% chance of happening in any given year. The compromise would be for a plan that protects between that and a 100-year event, which has a 1% change of occurring in any given year. The in-between option would cost an estimated $32-$40 million, in line with the original Variant 1 concept.

Staff did not make a suggestion about which option council should pursue, except to say that a flat-bottom detention area was “not recommended” because it “would likely have a large area of standing water during much of the year and (require) other trade-offs including the aesthetics, usability, drainage, maintainability and ecosystem function.”

Council also needs to decide how quickly to move through annexation. Members this fall requested more public engagement than is typically required. But the staff-dubbed “enhanced annexation” process would extend through 2020; council would prefer to finish this year.

To do so would limit the amount of community feedback to a Be Heard Boulder questionnaire and whatever comments are received while various boards consider CU’s application. Public comment would also be allowed during hearings before planning board and city council, both of which must sign off on the agreement.

To accelerate the annexation for a mid-2019 approval would also mean leaving certain details in flux. Final design of the flood work won’t yet be complete; the footprint is liable to change. Open space and water rights deals may not be finished by 2019 either, rendering open space and water boards unable to weigh in.

A quicker schedule is “aggressive for annexations of this size and complexity,” staff noted.

One other unknown: if the state will support to project in its current form. The land needed to build the flood wall lies in the Colorado Department of Transportation right-of-way along U.S. 36. CDOT previously gave approval but, staff noted, “current CDOT staff have to date been unwilling to recommit to supporting the project and staff continue to escalate discussions.”

“Their change in approach presents a risk to the flood mitigation project and annexation progress. If negotiations with CDOT are not successful, any floodwall or berm located outside of CDOT right-of-way parallel to US36 on the adjacent OSMP property would result in environmental impacts to sensitive species and require consideration of a disposal of OSMP land.”

CDOT has since January 2013 communicated with Boulder that it would consider allowing the right-of-way for flood mitigation, spokesman Jared Fiel said via email, but there are a “number of reasons why CDOT was reluctant, including lack of space and design constrictions for future US 36 roadway/bikeway improvements.”

In the elapsing six years, more issues have arisen, Fiel said. Those include concerns that using the roadway as a flood control feature would cause the enbankment to collapse, and that the liability during an event may be “too high” for CDOT and the Federal Highway Administration.

Furthermore, Fiel said,”CDOT and Federal Highways cannot allow a flood control structure on Right of Way purchased with federal dollars.  There may be other design alternatives that do not utilize CDOT Right of Way that could accomplish the same goal.”

Boulder and CDOT officials plan to meet Feb. 12 “to discuss all of this,” Fiel said.

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

Author’s note: This story has been updated twice, once to include comments from CDOT, and again to include comments from CU and to clarify that the university expects 129 acres of land for development, which includes 30 acres for athletic fields. 

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

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