Sealaska tackles massive project to protect Juneau-area communities from catastrophe

Juneau, Alaska — Construction teams are working fast to keep downstream communities safe from glacial outburst flooding.

Every August, the Mendenhall Valley above Juneau, Alaska, grapples with flooding – sometimes catastrophic – when the Suicide Basin dammed within the Mendenhall Glacier releases rainwater and snowmelt downst

This year, Sealaska’s construction team is working to protect the at-risk downstream communities, including Juneau.

“We work all over the country, and we’re proud to be doing this critical project right in Sealaska’s home territory,” said David McQueen, general manager of Sealaska’s construction arm. “The situation is complex, challenging and high-stakes – the kind of work we’re best at. Solving problems in difficult environments is our specialty.”

The annual flooding, known as glacial outburst flooding, occurs when a dam containing a glacial lake breaks. That happens in this case in later summer, when the Mendenhall Glacier melts enough to unleash the basin.

In 2023, a glacial lake outburst at Mendenhall’s Suicide Basin destroyed several structures along the Mendenhall River as the water rushed downstream. The record flooding prompted city officials in Juneau to issue an emergency declaration. Record-breaking flooding from Suicide Basin also occurred in 2024, when nearly 300 homes were damaged.

To prevent another catastrophe, the US Army Corps of Engineers (USACE) hired Sealaska to install 14,000 linear feet of barriers, more than 90,000 tons of rock armoring and earthen berms for water diversion. The HESCO barriers Sealaska is installing are rapidly deployable, earth-filled containment systems. Often described as giant, reinforced “super sandbags,” they consist of an outer collapsible wire mesh frame lined with heavy-duty fabric.

In addition, Sealaska is doing the dangerous work of chopping up trees and other large debris in the river after previous flooding so these hazards can’t do more damage downstream.

Between Sealaska staff and subcontractors, a 60-person team is working on both sides of about four miles of the river with a plan to finish before the flood threat rises in August. The work requires manual labor and coordination to move and place more than 1,500 tons of material a day. Subcontracted crews are building earthen berms and installing rock armoring along the river. The fill material in the HESCO barriers being installed by in-house crews must be manually compacted using human feet and small hand tampers. The HESCO barriers are a temporary solution to address the immediate flood risk. USACE is working on permanent solutions.

An important element of the project for Sealaska is hiring locally and ensuring teams include a high percentage of Alaska Native talent, said Sealaska Senior Project Manager Heath Barger.

“As a shareholder, former intern and past scholarship recipient, I recognize the importance of creating these kinds of opportunities,” Barger said. “About a quarter of our skilled crew is Alaska Native, which is something we’re proud of.”

This flooding is a threat with no end in sight.

Glaciers in Alaska have been experiencing a steep decline since the late 1980s, according to the state’s Department of Geological and Geophysical Surveys. Globally, glaciers are at risk of significant ice loss due to climate change, scientists say.

Glaciers around the world lost an estimated 7,211 billion tons of ice between 2000 and 2023, equating to an average annual loss of 301 billion tons, according to a Nature study published in February 2025. The rate of ice loss has increased by about 36% in the past two decades, the researchers found.