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Challenges include ecological issues

Posted: Monday, July 29, 2002

The closest the city of Kenai has come to making its dream of a sea wall and coastal trail a reality was in 2001 when the city applied for permits from the U.S. Army Corps of Engineers, the Alaska Department of Environmental Conservation and the Alaska Department of Fish and Game to begin construction on an erosion control structure that incorporated a Kenai River coastal trail.

The application was turned down, due to a list of unanswered questions and concerns submitted by various government entities. The entities, including the Environmental Protection Agency, DEC, Fish and Game and the National Oceanic and Atmospheric Administration, raised several ecological issues regarding the environmental impact the proposed sea wall may have on the river, the Kenai River Flats and the surrounding area.

Peratrovich, Nottingham and Drage Inc., the engineering consultants hired by the city to research, design and submit the project for permits, was given an opportunity to respond to those concerns. However, the firm did not have all the information needed to satisfy agency reservations about the project.

The following is a list of some of the main ecological issues that have been raised about the sea wall project:

Harming fish and wildlife habitat.

The concern: The Kenai River estuary and the Kenai flats support at least 26 species of fish, various marine mammals and numerous migrating and nesting birds. According to the EPA, erosion and transport and deposition of sediment in the river and at the river mouth renews habitat in the mouth of the river. Construction of the proposed sea wall could change flow, erosion and deposition of sediment patterns in the river, as well as possibly degrade the wetlands.

Engineering firm's response: The design of the project focused on minimizing the environmental impact of the sea wall and coastal trail. For instance, the proposed trail was set as high as possible on the beach and was realigned at its north end so the amount of fill required below the high tide line would be minimized.

Disturbing the natural course of the river.

The concern: Using armor rock (large boulders) below the high tide line would harden that portion of the river bank. Hardening the bank may deflect energy to the opposite bank and cause erosion in a different area, possibly in the ecologically important wetlands. It may change the pattern of the river altogether.

Engineering firm's response: The project will not significantly alter flow patterns in the river because the amount of proposed trail fill in the river mouth is small compared to the rest of the flow area in the river.

Depleting sand dunes.

The concern: Stopping the erosion of the bluff in that area will deprive the beach dunes at the mouth of the river of sand.

Engineering firm's response: A University of Alaska study of sediment transport in the mouth of the river found that most of the sand that feeds the dunes does not come from the area of the bluff proposed to be altered. Additionally, there is a surplus of sediment in the river mouth, so even if erosion of that portion of the bluff was stopped, the dunes would still have sand.

There were some issues the engineering firm couldn't answer that will be addressed by the Corps of Engineers study. For instance, the firm did not conduct fish and wildlife habitat or biological studies that the EPA and Fish and Game require for permit approval. A detailed engineering and economic evaluation of potential project alternatives to the sea wall option also was not prepared by the firm, although it did investigate other options in its research. Additional hydraulic study on sediment transportation in the river will similarly be left to the Corps study.



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