Ketchikan Runway Safety Area Expansion
Alaska Department of Transportation & Public Facilities
Hart Crowser addressed fisheries, marine, wetlands, and wildlife issues associated with several alternatives for expansion of the Ketchikan Airport Runway Safety Area (RSA). All build alternatives would result in impacts to one or more anadromous fish streams and associated estuaries. We prepared resources reports for adaptation into the NEPA EIS. We provided biological input to the interagency team on the design of 2,000 feet of a new engineered channel for Government Creek, a significant salmon spawning stream. Our studies demonstrated that the proposed mitigation would successfully offset impacts of this transportation project on fish and other aquatic resources.
The channel floodplain was excavated into bedrock and till with cuts to 80-feet deep. A sinuous stream channel and several off-channel sloughs were then excavated into the new floodplain. In the design, we established a natural sequence of riffles and pools using existing bedrock and boulders weighing up to 10 tons. Large woody debris (LWD) and boulder clusters were also installed to trap gravel and to provide instream habitat for spawning and for juvenile salmonids. At the stream mouth, we designed a new brackish marsh estuary to provide a gradual and natural transition from the new stream channel into the marine environment of Tongass Narrows.
Before construction, our biologists monitored the stream, eelgrass beds, salt marsh, and habitat utilization, then implemented a long-term monitoring program to assess the effectiveness of the newly designed habitat features. During construction, we visited the site frequently to work with the project managers (client and contractor) and equipment operators to refine the details of the design implementation. We also monitored stream and estuarine habitat (including eelgrass and salt marsh) to assess effectiveness and longevity and utilization by juvenile/spawner salmon populations following construction. Our work included studies demonstrating that the implemented mitigation and restoration successfully offset impacts of this transportation project on fish and other aquatic resources. The new stream and estuary have been shown to support heavy spawning by pink salmon and rearing for coho salmon and Dolly Varden char, a close relative of the bull trout, which is an Endangered Species Act-listed species. Salmon were documented spawning in the new stream channel within two weeks of flow diversion, and salmon spawning and rearing in the new stream has been robust since construction.