JOINT BASE ELMENDORF-RICHARDSON -- Juneau citizens will see new infrastructure poised to mitigate the flood risk of the annual glacial lake outburst flooding event caused by Mendenhall Glacier near Back Loop Road. A new earthen berm is in the works due to the partnership between the U.S. Army Corps of Engineers – Alaska District, U.S. Department of Agriculture’s Forest Service and City and Borough of Juneau.
On June 5, a contract modification was awarded to Sealaska Corp. to construct an earthen berm extending about 1,100 feet east from the Back Loop Bridge. The berm will follow the general alignment of the existing high ground to provide flood protection for Back Loop Road and downstream portions of the community. Specifically, the new infrastructure is designed to prevent overtopping on the road and is located on Forest Service managed land. Construction will start immediately.
“This new berm is an example of what can be achieved in a short amount of time when federal agencies and stakeholders have different missions but share a common goal like bringing flood risk mitigation measures to Juneau,” said Col. Jeffrey Palazzini, commander of the Alaska District. “We all understand what is to come in August, and we thank our partners at the Forest Service, CBJ, and Tlingit and Haida Indian Tribes for their continued urgency, coordination and partnership.”
"It’s great to see the kind of progress that comes from federal and local agencies collaborating on shared goals like public safety,” said Michael Downs, Juneau District Ranger for the Tongass National Forest. “The Forest Service is committed to the safety and enjoyment of visitors, locals, and staff at all public lands we manage.”
“Preparing for annual glacial lake outburst floods takes strong partnership and shared commitment,” said Tlingit & Haida President Chalyee Éesh Richard Peterson. “We appreciate the collaboration between Tribal, federal, and local partners to help protect our community and improve flood resilience.”
As part of the Public Law 84-99 Advance Measures agreement, CBJ requested that USACE construct about 1,000 linear feet of temporary flood mitigation barriers along the lake side of Back Loop Road due to the potential for overtopping of the road at higher flood levels and subsequent inundation risks to nearby neighborhoods and the Mendenhall River Community School. After further consideration and collaboration with USACE and USFS experts, an earthen berm was identified as a more resilient temporary mitigation measure that would be less vulnerable to damage from vehicle traffic and require less maintenance and future repairs.
“Protecting the Mendenhall Valley from the threat of annual glacial lake outburst floods requires collaboration and informed problem solving on all fronts,” shared Katie Koester, city manager for CBJ. “With the USFS, USACE and CBJ all working together, we are able to be more nimble, responsive and effective in this effort. We truly appreciate the responsiveness from these committed agency partners.”
The berm will impact an area of about two acres of Forest Service managed land adjacent to Back Loop Road between Back Loop Bridge and Chelsea Court. The berm will have a height of 10-12 feet with a width of 50-60 feet once finished. The effort will include site preparation and clearing, construction of the embankment itself and, finally, stabilization activities. Some timber will be marked for salvage and public use as well.
Currently, USACE is leveraging its expertise and authorities to deliver flood risk reduction, that builds on the immediate actions already taken, to provide additional protection this year. The new earthen berm is anticipated to be complete by July 15.
For more information about Back Loop Bridge Trailhead closure, please visit https://www.fs.usda.gov/r10/tongass/alerts/back-loop-bridge-trailhead-emergency-closure-mendenhall-glacier-recreation-area.
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