What to do with Eyak Lake’s failing weir?

Engineers will discuss Cordova’s options at July 19 meeting

The Eyak Lake weir. (Feb. 21, 2020) Photo by Zachary Snowdon Smith/The Cordova Times

The 1964 Good Friday earthquake affected geography all over Cordova, including at Eyak Lake, lowering water levels and threatening to turn the area into a swamp. In 1972, to preserve productive sockeye spawning territory and other natural assets, a weir was constructed spanning the lake. A weir is a low barrier that helps regulate water levels — in this case, keeping Eyak Lake’s water levels from falling too low.

Now, after almost five decades, the weir is gradually failing, and water levels have fallen. If the weir fails completely, it could impact nearby highway bridge infrastructure or nearby waterfront properties, said Kate Morse, program director for the Copper River Watershed Project.

Since 1972, it’s been unclear who is responsible for maintaining the weir. That, and a lack of consistent documentation, have stymied past attempts to address issues with the weir. Now, CRWP and the U.S. Forest Service are leading a renewed effort to fix, upgrade or redesign the weir before it gives out completely. To that end, CRWP has requested the public to participate in a 12-question online survey at cdv.tiny.us/weir. Additionally, a public discussion with engineers employed by the firm DOWL is scheduled for 5:30 pm. on Monday, July 19 at the Cordova Center Community Rooms.

CRWP has submitted a proposal for design and construction of an improved or replacement weir to the Exxon Valdez Oil Spill Trustee Council, and plans to submit a more detailed proposal in August. Before then, organizers must resolve whether renewing the weir would simply amount to patching it up, or would involve redesigning it completely. While the existing weir has controlled water levels reasonably well, its sheer face obstructs fish passage. A redesigned weir, using stone riprap to create a more gradually sloping barrier, would allow fish to easily travel in and out of the lake. Some designs requiring more material, and being logistically complicated to construct, could require less ongoing maintenance after construction, Morse said.

Additionally, the existing weir features a boat slot that allows vessels passage from one level to another. However, excluding a boat slot could simplify designs for a renewed weir, Morse said. Whether Cordova boaters consider the weir’s boat slot useful is one of the questions project organizers seek to answer through their online survey and through the July 19 public meeting.

The Alaska Department of Fish and Game and the Alaska Department of Transportation and Public Facilities are also partners in the project, Morse said.