The devastating floods that struck Boulder in 2013 catalyzed the urgency for a flood mitigation project on the CU South property. Credit: City of Boulder

This November, Boulder voters will decide whether to repeal an agreement between the city and the University of Colorado that sets the terms for developing the South Boulder property known as CU South. 

At stake is a flood mitigation project designed to protect about 2,300 residents who live in the South Boulder Creek floodplain. 

The latest fight is rehashing a fraught history surrounding the project and the land, cherished by many, upon which it would be built. It is also reigniting a debate over the complex tradeoffs involved in managing flood risks connected to climate change.

The annexation agreement allows the city to use CU Boulder’s property to build an up to 10-foot-tall concrete spillway along U.S. 36 to prevent floodwaters from roaring across the highway and into residential areas. In exchange, the city is allowing the university to build housing and academic facilities, as well as a 3,000-person stadium, and providing water and sewer services. 

The flood plan has been discussed since at least 2001, after studies revealed downstream flood risks. But the urgency for the project didn’t catalyze until 2013, when a days-long deluge caused South Boulder Creek to overtop U.S. 36 near Table Mesa, sending waist-deep water into neighborhoods and the Frasier Meadows retirement community. 

Under mounting pressure from South Boulder residents and after painstakingly weighing several designs, the city council in June 2020 directed city engineers to begin designing a 100-year flood mitigation project. The project would reduce the flood risk for approximately 1,100 homes located in the 100-year floodplain — meaning those homes have a 1% risk for flooding in any given year. 

The city still needs federal, state and city permits to break ground. Construction on the $66 million project could start as soon as 2024, and last about two years. 

But as the city moves ahead with the plan, some residents want to start over. 

Among the issues they have raised is that the flood project made possible by the annexation agreement should protect more people. The deal “fails to address climate change and 500-year flooding as recommended by experts,” a recent campaign mailer states.

The larger, 500-year project would protect 800 more dwelling units than the 100-year plan, according to city estimates. Those homes have a .2% chance of flooding in any given year. 

At one time, all members of the Boulder City Council from across the political spectrum supported a 500-year flood project, at least conceptually. So did CU Boulder. But the project that everyone wanted ran into major hurdles — technical, political and philosophical. 

The 100-year flood project the city is now pursuing is the result of years of push and pull between the perfect and the possible. 

The latest attempt to undo the annexation and revisit the flood design follows a long history of what-ifs and hard-fought campaigns to halt its construction — and a decision by some to put the past aside and get something built. 

“There’s no perfect solution,” Councilmember Mark Wallach said during a meeting in which the 100-year design was approved. “I’m not sure there’s even a good solution. There’s only a choice that each of us has to make and will make to the best of our ability.”

The city is planning to build a spillway on the CU South property in South Boulder. The $66 million South Boulder Creek flood mitigation project is one of many the city is planning. Credit: John Herrick

Pushback from CU Boulder: 129 acres or bust

In 1996, despite opportunities for the city to purchase the CU South property, the university bought the former gravel mine for $11 million with big plans to develop it. In the years since, the university fought off legal challenges by Boulder County commissioners and a 2006 ballot measure by residents to block development. 

Meanwhile, the university sought annexation into the city because it needed its water and other services. But the City of Boulder refused to discuss annexation until it finalized a flood plan for South Boulder Creek. In 2015, two years after the destructive 2013 floods, it completed a South Boulder Creek master plan, which proposed building a floodwall along U.S. 36 as the most cost-effective option. 

To build the project, the city required the university’s land. And so the annexation talks began. 

In 2017, the Boulder City Council approved land-use code changes that would allow the university to build on about 129 acres of the 308-acre CU South property. Much of the remaining land was set aside for open space and the city’s flood mitigation project. 

In 2018, city officials presented councilmembers six different flood-control concepts using U.S. 36. All councilmembers wanted the flood project to include a 500-year level of protection, in part to prepare for a changing climate. 

“This is going to affect more generations than any of us can even fathom,” Councilmember Mary Young, who opposes this year’s annexation referendum, said. “Conditions are changing, with potentially drastic environmentally different weather patterns.” 

Councilmembers disagreed on the finer details, however. Most preferred a plan that, in the event of a flood, would inundate the dry land outside the floodplain, effectively creating a “detention pond” on the same chunk of property the university wanted to develop. Some councilmembers hoped by greenlighting a project that would push floodwaters onto this dry land, the university would reduce the 129 acres it sought to develop. They suggested trading city land elsewhere for university housing. 

“I’d be open to other places, too, if CU needs additional housing,” said Councilmember Lisa Morzel, who had sought to pass the 2006 ballot measure aimed at blocking the CU South annexation. 

University officials pushed back. They suggested a different 500-year flood mitigation design that wouldn’t eat into their 129 acres. (It would have required modifying the U.S. 36 bridge and, according to information later revealed, the state would have likely rejected it.) 

“There are viable options,” Frances Draper, CU’s Vice Chancellor for Strategic Relations who died of cancer in 2021, told councilmembers. “We prefer to do this in partnership, rather than being put in a corner.”

Despite opposition from the university, on Aug. 21, 2018, a majority voted to direct city engineers to begin designing the 500-year project that CU Boulder opposed. 

In response, the university wrote a letter restating its opposition. It later suggested allowing the project to proceed if the city allowed the university to build in the southern part of the property, which was located in the floodplain, so that it could build on a total of 129 acres. To make this possible, it asked the city to truck in dirt and gravel to raise the land out of the floodplain. (City staff later estimated the fill alone would cost $34 million.)

To avoid a drawn-out fight with the university, and given the pressure from downstream residents to get the project built, the city council directed engineers to come up with a 500-year flood design that ensured the university had 129 acres. They also asked the city to study a 100-year flood concept, as a potential back-up option. 

Then came another, separate hurdle. 

To build any of the flood projects under consideration at the time, at any level of protection, the city would need a permit from the Colorado Department of Transportation, which owned the right-of-way along U.S. 36. The agency imposed two requirements that, according to the city, created potential insurmountable obstacles. 

First, the agency told city officials it would not allow any above-ground structures in its highway right-of-way. This meant the city had to build the project on city open space, potentially triggering an open space “disposal” process requiring approval from the Boulder City Council and Open Space Board of Trustees. Further, to build the 500-year project, the city would have to destroy about five acres of open space, including habitat for the Preble’s meadow jumping mouse and Ute lady’s tresses, both of which are listed as threatened under the Endangered Species Act. (The current 100-year plan requires destroying less than one acre, making it more likely to be approved.) 

Second, the Colorado Department of Transportation told the city it did not want any modifications made to the South Boulder Creek bridge. Under the 500-year concept, additional water would be sent under the bridge, according to city engineers. City officials worried the additional high-velocity water might affect the structure of the bridge, making it more difficult to get state approval.  

Considering all this, Joe Taddeucci, the city’s director of Utilities who was managing the flood project, told councilmembers he foresaw major permitting challenges with any 500-year design. 

“I just concluded there is no way,” Taddeucci said. 

On June 16, 2020, the city council voted unanimously to direct city engineers to design a 100-year flood mitigation project. 

It is designed to hold back floodwaters from the South Boulder Creek, inundating an area along the highway up to the edge of the university’s tennis courts, according to a July 2022 preliminary design report. To prevent flooding, the spillway would gradually release the water through a pipe, culverts, a wildlife underpass and the bridge over South Boulder Creek. 

The Boulder Nordic Club, a local nonprofit, grooms CU South for Nordic skiing. Credit: John Herrick

Alternative designs 

Some residents questioned the opinions of city officials. They cited studies by engineers hired by the city suggesting that, under certain scenarios, the 500-year project would not affect the South Boulder Creek bridge. 

Other residents provided their own flood project concepts. In 2018, Gordon McCurry, a hydrologist and member of the city’s Water Resources Advisory Board, suggested building a series of detention dams upstream of U.S. 36. City engineers said such a project would still require a floodwall at the highway. Other upstream ideas would be more expensive and impact more open space, according to a Jan. 5, 2021 analysis

Some residents wanted to designate CU South as open space and have campaigned on concerns that even the 100-year floodwall might block views of the Flatirons. They’ve suggested the university build on a plot of land north of the city known as the Area III Planning Reserve. The university opposed that land swap, in part because the land was not eligible to be annexed. (The city plans to study whether to connect water, sewer and other services to the area.) 

Ideas continue to emerge. During a debate on Sept. 30, 2022, Steve Pomerance, a former city councilmember supporting the campaign to repeal the annexation agreement, suggested residents floodproof their homes. One purpose of this might be to buy time to force concessions from the university as part of the annexation.

“Let CU sit there,” Pomerance, who lives near the Chautauqua neighborhood, said. “And when they finally realize it’s going to be 50 years before they even get considered to be annexed, maybe they will start to deal.”

Suggestions of delay have frustrated residents living in the South Boulder Creek floodplain. For years, they filled rows at City Hall wearing orange shirts stating “protect us now.” They presented videos of rivers flowing down their street.

“I am tired of talking about engineering,” Laura Tyler, a member of the South Boulder Creek Action Group, told councilmembers at a June 2020 meeting. “It’s my opinion that the engineering conversation is actually a proxy for this bigger conversation about land-use issues.” 

Rachel Friend, a South Boulder resident whose home was flooded in 2013, was later elected to the Boulder City Council in part on a platform of hastening the project’s completion. She opposed proposals that could cause delays, including a land swap. 

“Anytime we get close to nailing it down, we move the goalpost,” Friend said during a February 2020 council meeting. “It’s a delay. And it’s saying people’s lives are not that important.” 

Those holding out hope for the 500-year project argue it’s better suited for more severe weather that climate change will continue to unleash. A recent campaign mailer claims a vote for the referendum “means implementing one of the 500-year plans that will protect all citizens against bigger floods.” At this point, the larger project would take more time to build and its approval is unclear. 

When Taddeucci thinks about climate change, he thinks about the city’s 16 drainages. More than 2,600 structures are located in the 100-year floodplain across the city. About 10% of those structures are in the South Boulder Creek floodplain. 

“One of the ways we can combat climate change is to build as many projects as quickly as we can,” he said in an interview. 

Critics of the current 100-year project argue it would provide a false sense of security. They cite recent floods across the U.S. that the current project would have done little to stop. 

Taddeucci said no one project will fully protect residents. He referenced the Dec. 30, 2021 Marshall Fire, which, propelled by 100-mile-per-hour downslope winds, destroyed more than 1,000 homes and upended thousands of lives. 

“There is a tipping point for all of these emergency scenarios where we do the best we can proactively in advance and with mitigation,” he said. “As events become more and more extreme, the attention turns to evacuating people.”

John Herrick is senior reporter for Boulder Reporting Lab, covering housing, transportation, policing and local government. He previously covered the state Capitol for The Colorado Independent and environmental policy for He is interested in stories about people, power and fairness. Email:

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  1. A static map would be very useful here, something that is easier to look at than this link.
    It’s difficult to get a good look at the South Boulder Creek even when you google it; there are few maps out there. Also worth knowing WHERE the majority of the 1,100 homes are located: mostly Frasier Meadows? Is that who’s opposing 2F?
    Appreciate this reporting on such a confusing issue! Every time I walk through the CU south trails (almost daily), I wonder how in the world a new development with additional apartments is a good idea in the middle of a floodplain. It just doesn’t make sense when you’re out there it really feels like it should stay a natural wetland, not concrete.

  2. This article points out that a special interest group, representing only 260 structures that would be protected, helped thrust this issue and Rachel Friend to city council and pushed for a plan considered inadequate by most participants, except maybe Joe Tadeucci. See Ben Binder’s google video on CU South. That is the best encapsulation of the weaknesses of this plan. The story does not talk about our available funds for flood mitigation, or how much of that would be used for this project, for just 250-260 structures. I think it is half of all the monies available to our entire town for the next 10 years! Everyone else can fight over the remaining 50% of our funds for the next decade. Tadeucci is no flood expert, no flood mitigation expert, no land use expert, no engineering expert, no hydrology expert, and certainly no environmental expert.

    Also, nowhere does the story discuss the fact that with 750,000 sq ft of development, a sports arena, and residences, roads — that is a lot of land that is not absorbing water. Where does it go? To its credit, the story looks to the future of climate change, and the facts that we are looking at 100-year events (11 1,000-year floods in our country in the last year). Yet it still lands on Tadeucci responding about the radical fires we have experienced as being some kind of justification for an inadequate plan. While CU stubbornly held on to every demand, we gained very little if anything. I hope Boulder votes yes on 2 F.

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