Fish Passage Project Brings Need for Retaining Wall

In Port Angeles along US 101, the Washington State Department of Transportation (WSDOT) delivered another fish passage upgrade at Ennis Creek, restoring natural stream conditions and reopening habitat for aquatic life.

But as the plans took shape, it became clear that conditions above the fish passage would require another piece of infrastructure: a retaining wall.

Originally designed as a conventional mechanically stabilized earth (MSE) system, the wall was later reevaluated and, in close coordination with the contractor Kiewit, redesigned as a stem retaining wall.

What followed marked a first for WSDOT and offered a fresh look at alternative retaining wall systems for agencies across the region.

A traditional MSE wall would have required extensive excavation, driving up labor, time, and complexity. Plus, in a tight corridor under live traffic, that approach becomes inefficient and difficult to stage.

A gravity wall wasn’t a fit either. Height and loading constraints limited its feasibility.

At the same time, the solution had to meet strict DOT requirements. Stem wall systems were not standard for WSDOT, meaning any design deviation required additional engineering and approval.

Overall, the project needed a system that could reduce excavation, simplify construction, and still perform structurally in a demanding environment.

To forego the conventional approach, a Gravix retaining wall became the answer, marking the first approved use of the system by WSDOT.

Instead of excavating large volumes of soil to accommodate reinforcement layers, the Gravix system allowed slot construction. Narrow cuts were made, the wall pieces were set, and backfill was placed in smaller, controlled sections. This approach reduced excavation, lowered labor demands, and simplified installation within a tight footprint.

The finished wall measured 201.5 linear feet with approximately 2,180 square feet of surface area, consisting of 55 precast pieces. Of those, 25 were custom top panels, manufactured at precise angles to follow elevation changes and deliver a clean, continuous profile along the roadway.

The result is a structurally efficient retaining wall that supports the surrounding earth while meeting project constraints and WSDOT requirements.

Need a Gravix retaining wall for your next project? Contact Jensen Infrastructure today.