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As Mother Nature nibbles away at the Kenai bluffs, the Army Corps of Engineers is whittling down the mountain of work needed to assess the condition of the bluffs, study ways to halt the advancement of the elements on Kenai real estate and forecast the impacts of any abatement alternatives.

On Wednesday, a half dozen members of the Corps along with consultants from the Tetra Tech engineering firm met with Kenai City Council members in a work session to report on progress already made and the current status of the project.

The corps has said a number of things contribute to bank erosion at the mouth of the Kenai River, including wind, waves, foot traffic, overland drainage and river currents, but the primary contributor is groundwater seepage out of the bank face.

Design alternatives being looked at now focus on reducing the slope of the bluff by removing some soils from above the groundwater line, transferring that material to the lower half of the bluff -- also reducing the slope -- and placing armor rock at the foot of the bluff where it meets the river.

Tetra Tech Project Manager Krey Price said to try to keep the flow of groundwater underground, the design would have a terrace of sandy material above the seam that separates the upper soil from the clay layer below the groundwater table.

"This also becomes convenient for maintenance access or potential public use ... a birding trail," Price said.

Groundwater would be collected and kept 10 feet back from the face of the bluff, allowing it to flow out through rock material placed at the toe of the bluff.

Because of extreme wave action, particularly during winter storms off Cook Inlet, willow plantings for bluff stabilization at the toe of the erosion control earthwork would not suffice, according to the engineers.

"Rock is the way to go," said Pat Fitzgerald, Army civil engineer.

After deciding on rock, the Corps looked at what might happen to tidal flats across the river as waves bounced off the armor rock, but studies showed the wave energy would be dissipated by the varying angles of the rock, making any impact across river negligible.

Another concern was that sediments naturally flowing out of the Kenai River might be providing nourishment to the Kenai sand dunes, but, according to Fitzgerald, "the major source of dune nourishment is along Cook Inlet from the north."

After outlining a number of concerns and determinations, Fitzgerald told the council members the Corps has money for study and design at this time, but no money for construction.

"Hopefully we'll get the money and be able to help out the city," he said.

According to the Corps report, the total cost of the bluff stabilization project, including the cost of acquiring real estate as the slope is tapered back and planting vegetation on the slope face, comes to nearly $26 million.

Kenai residents have already voted to approve issuing $2 million in municipal bonds toward funding the project, and the Alaska congressional delegation has appropriated $1.5 million.

Although Fitzgerald said the Corps does not have money for construction at this time, the council members were told Sen. Lisa Murkowski has been a proponent of the project.

Further wave analysis work could also reduce the cost of the project by reducing the amount of armor rock needed to stop the erosion. The armor rock is one of the costliest components of the project.

Phil Hermanek can be reached at phillip.hermanek@peninsulaclarion.com.