City, tribe and Forest Service align on a ‘lake tap’ as preferred long-term USACE glacial outburst flood solution
- Jasz Garrett
- 24 hours ago
- 7 min read
There is no authority yet to build or fund the project, but the chosen alternative accelerates the publication of a technical report for public review by May 2026
By Jasz Garrett
Juneau Independent
A preferred long-term glacial outburst flood solution for the U.S. Army Corps of Engineers to study was announced Friday by local leaders, following meetings this week between the federal agency leading the project and its community stakeholders.
The best option was a Suicide Basin lake tap, according to the U.S. Forest Service, the Central Council of Tlingit and Haida Indian Tribes of Alaska, and the City and Borough of Juneau. This means boring a tunnel through Bullard Mountain so the basin’s water can drain more slowly into Mendenhall Lake.
“Instead of having this bathtub that fills up in Suicide Basin, and then you pull the metaphorical plug on the bottom, and then you get this huge amount of pressure and 16 billion gallons of water that all rush out and have to move through a system in 48 hours, you have this continuous flow probably in the order of 800 cubic feet per second,” said Denise Koch, CBJ’s director of Engineering and Public Works, in an interview Friday.
“Just as a reminder to the 2025 GLOF, the best estimates are that that was 52,000 cubic feet per second,” she said. “So orders of magnitude slower — 800 cubic feet per second, that is just a consistent flow, so that you're just routinely draining the basin, and it doesn’t have the opportunity to fill all the way up.”
The lake tap is not yet the official solution since further review is needed, according to Koch. But she said it appears to be the most cost-effective and safest option presented, with early estimates ranging from $613 million to $1 billion.
“There’s a huge contingency factor because they’re just at the beginning of refining these different options,” she said.
A USACE spokesperson said last week the three days of closed-door meetings were intended for technical presentations and the review of the five options, not to reach a decision on a preferred alternative or announce it. However, plans changed when the collective preferred decision was announced Friday.
The other four alternatives reviewed over the three-day charrette included flood-control dam(s), levees or floodwalls, relocation, and a hybrid option of dams and levees. Koch said the cost for the other options was $2 billion or more.
The tunnel would have an 8% slope and be gravity-fed, with simpler operations and maintenance than other proposed options that include more electrical and mechanical components, Koch said.
The most cost-effective option also has the lowest safety risk, does not require property relocation, and has a smaller environmental and cultural footprint, according to CBJ and Tlingit and Haida.
Funding and approval for the project’s construction still do not exist, but the aligned decision by community stakeholders will allow USACE to focus its technical study efforts on one preferred option from the five presented, according to Koch.
“The reason it’s an important step is this will enable the Army Corps and their contractors to be more efficient as they move forward in their technical study, because they’ll now just be focusing on the lake tap versus really looking deeply into five to 10 different options,” she said. “And the technical study is really important, because that’s a kind of a platform or a springboard for trying to advocate for money and authority to actually build a solution.”
The technical study is expected to be released by May 2026, with another public comment period expected on its findings. Participants in this week’s charrette reviewed public input from the 30-day public comment period in November.
The lake tap solution itself could still take up to six years to complete, Koch said. She also called it a 50-year solution, since scientists attending the meetings estimated that future basins still under the ice will not pose a problem before then.
Koch said on the second day of the flood meeting, the three stakeholder groups broke off to discuss their preferred alternative based on an overview USACE provided the day before. Then each group presented its favored solution. Koch was the spokesperson for the CBJ group.
“Risk is evaluated both in terms of the ability of a solution to reduce risk, such as loss of life, loss of property, economic risk – it also considers the risk of failure of the potential solution itself,” Koch said. “So, for example, one different and really important difference between a lake tap and a dam is that although Army Corps has very extensive knowledge on how to build and operate dams, and it’s a well-known and tested technology, the risks associated with dam failure can be catastrophic.”
She said the failure of a lake dam could trigger a flash flood worse than the glacial outburst flood itself. But in the case of the lake tap, if a glacier or rock partially or entirely blocked the inlet on the lake and the basin, that failure would revert to the original risk of the current flood.
“So the risk isn’t worse than the no-action alternative, whereas the risk is worse if there’s a dam failure,” Koch said.
Also involved in the meeting were AECOM technical experts contracted by USACE, who have tunneling expertise in the Alps and other places around the world, Koch said. She added the safety risks associated with the lake tap center on its construction and worker safety, since blasting of the mountain will be involved. The outlet will likely be between Nugget Falls and the face of Mendenhall Glacier, with restricted access.
Sabrina Grubitz, the public safety manager for Tlingit and Haida, was the tribe’s spokesperson. Like the Forest Service and the city, her organization’s group also chose the lake tap option.
“We really looked at making sure that our cultural sites, our cultural identity, was not mutually impacted. We wanted to make sure that those were honored and acknowledged through this process,” she said. “We wanted to make sure that we were arriving at a solution that was expedient, but also made sense for the community and our tribal citizens. Looking at all of the different options, the lake tap was the one that, at this point in time, with the data that we were presented, appears to have the smallest footprint of impact within the area.”
She said a large factor was that there would not need to be relocations of citizens and the tunnel’s drainage addresses the root of the cause. Grubitz said environmental and cultural sensitivity studies will take place.
“The way that the lake tap option is designed is it would release water in a way that’s passive, and it would not require the movement or adjustment of a lot of other sites that are sensitive or visually impair what we can look at for the glacier,” Grubitz said. “The lake and the river are obviously culturally important to our people. We’ve been accessing in that space for years, and so making sure that we still have access to it and it’s not impeded, or it’s impeded for the least amount of time, was important for us.”
She said a co-stewardship agreement of the Mendehall Glacier Recreation Area the tribe established with the Forest Service in 2023 helped develop the working relationship present in this week’s meetings. The agreement allowed Tlingit and Haida to participate in shared decision-making for Juneau’s most popular tourist attraction.
Jökulhlaups from Suicide Basin have occurred in Juneau annually since 2011, but they became a priority issue for city leaders when record flooding in August of 2023 severely damaged dozens of homes along the Mendenhall River. A much higher flood in August of 2024 damaged nearly 300 homes, prompting the installation earlier this year of a semi-permanent levee of HESCO barriers.
Those barriers protected most homes from yet another record flood this August. But since the first record flood, city and USACE officials have agreed a long-term solution is necessary since glacier melting caused by climate change means flooding may continue to be an annual threat for decades.
Koch also pointed out scientists say the severity of the floods is expected to worsen, meaning time is of the essence. It was more than just a discussion of risk – there was also a discussion of timelines to complete a construction project, and the lake tap had the shortest one.
“That is really, really critical because while we’ve been saying all along that CBJ has been pursuing a parallel path on this short-term flood fighting and this long-term enduring solution, the longer it takes to find an enduring solution, the longer we have to flood fight,” Koch said. “And the flood fighting itself comes with its own risks. It gets more and more challenging to flood fight as the GLOFs become more severe.”
USACE officials have previously stated a long-term solution could take a decade or more to research and implement, and cost hundreds of millions of dollars. Most of the money would likely come from federal sources, which would have to be approved by Congress, although local municipalities are generally required to provide some matching funds.
The city and USACE signed an agreement on Oct. 30 specifying the federal agency would pay for and install an extension of the current HESCO levee before next year’s expected flood, with the city responsible for maintenance afterward. The existing barriers also need up to $1 million in repairs from this year’s flood, an indicator that a long-term solution is needed, since the barriers have an estimated effective lifespan of five to 10 years.
USACE officials also said at that meeting they planned to select a preferred long-term alternative as early as December, with an environmental review completed by May, to speed up the process toward a lasting solution.
“We’re still going to need the community and our congressional delegation, and our community leaders like President (Chalyee Éesh Richard) Peterson and Mayor Beth Weldon and City Manager Katie Koester just continuing to go to Washington, D.C., to get advocacy for funding and money to keep this project going, so it's just going to continue to require community attention and community support,” Koch said.
Grubitz said the tribe remains committed to working with the city and its community partners to move closer to an enduring solution. She added she does not think it’s common for local and federal governments to work closely with tribal governments and recognize sovereignty, and expressed gratitude for the tribe’s seat at the table.
“This type of situation has really brought us all together,” she said. “We have a goal that is something we’re all aiming towards, which is protecting the life and safety of all of our citizens in our residence together. It was incredible to see everyone come together. Just the unity within this process has been huge.”
• Contact Jasz Garrett at jasz@juneauindependent.com or (907) 723-9356.
