Engineers told the Kenai City Council on Dec. 3 that construction of a nearly mile-long bluff-stabilization berm along the Kenai River is finished and that monitoring and encouraging vegetation are the most practical next steps to secure the upper bluff.

","Ronnie McPherson, a civil engineer with HDR, described the structure as a toe-stabilization revetment placed to reduce erosion from waves, storm surge and river/sea ice. He said construction finished Oct. 11 and reported roughly 26,500 cubic yards of armor rock and about 36,000 cubic yards of core and bedding rock were placed across approximately 4,700 linear feet.

McPherson emphasized the design limits: the berm addresses toe erosion from water and ice but does not eliminate wind-driven or groundwater-driven bluff retreat. "The structure itself was designed to reduce and eliminate erosion due to wave action, storm surge, river and current, and ice," he said. He explained that geotextile composites and a graded bedding layer were used beneath armor rock and that an eight-foot inspection path was installed along the top of the berm for future access and inspections.

The presentation broke down how engineers project a range of future bluff positions by applying simplified slope profiles drawn from adjacent stable sections and Army Corps geotechnical work. McPherson described using multiple reference slopes (including the Army Corps’ 35–40 degree geotechnical range and observed adjacent slopes from 1.7:1 up to shallower profiles) and said the steeper of the observed adjacent profiles is likely the most realistic near-term outcome. He also summarized chronic versus episodic erosion: "By having the berm in place, the idea is that episodic erosion ... we hope is basically neutralized," he said, while chronic processes such as wind or groundwater-driven movement may continue until vegetation establishes.

On timeline and monitoring, McPherson said visible vegetation improvements could appear in one to two years and recommended an operations-and-maintenance manual with periodic surveys and visual monitoring of bluff position and vegetation cover. He cautioned against placing heavy equipment or trying to "force" large-scale fill on the bluff face, noting that adding new material or high-vibration machinery could worsen bluff stability.

Council members pressed on utilities in the zone, the structure's performance during a strong October tide event and whether ice plucking had been considered. McPherson said he received no reports of structural damage after the October storm and that ice was a controlling factor on the downstream sections; armor sizes on the downstream portion were selected to resist ice forces.

The council did not take action on the presentation; staff said the project files and presentation slides will be made available to council and the public.