March 9, 2021
Conservationists and downstream residents have reasons to worry about a debate over what is needed to make dams safe on three upper Icicle lakes.
The Icicle Peshastin Irrigation District, which operates two dams on Colchuck, and one each on Klonaqua and Square Lakes, is questioning deficiencies that the state Department of Ecology's Dam Safety Office cited after a recent inspection. On November 20, 2020 we described the state's report here in Safety issues raised at three Icicle dams.
The irrigation district is also asking the state to reconsider its classification of at least two and perhaps all four of these dams as "High Hazard," an assessment the safety office says it made based on national standards.
State safety inspectors concluded that Colchuck Lake's main dam and the dams on Klonaqua and Square lakes are in poor condition. Only the Colchuck Lake Saddle dam rated a condition of "Fair."
Both sides agree that remedial work is needed. The four dams suffer in varying degrees from age. But the debate is over how much work is needed, and whether a dam failure would pose as much of a downstream threat as the safety office fears.
The irrigation district claims that the small amount of water released by a failure, the length of time it would take to reach any residents, the time it would take for that water to dissipate, and the risks that any flood would cause serious damage are so small that a "high hazard" rating is not justified.
The work it is planning varies with the dam, but in all cases the irrigation district will be inspecting and possibly upgrading or replacing outlet pipes and gates. It also hopes to automate the outlets on all dams so they can be adjusted remotely, and to upgrade the log booms with artificial logs that are less likely to sink. At Square Lake it plans to fill the core of its rock and masonry dam with a concrete-like material. The leaky dam at Klonaqua Lake poses the biggest headache because it consists of old logs that are rotting. The irrigation district proposes to replace them with baskets of rocks placed in a mesh cage.
It is uncertain that these steps will satisfy the dam safety office. It claims that the dams "are in varying states of disrepair, with severe spalling, cracking, and other deficiencies seen on embankment walls and spillways." It also intends to require "that any undersized spillway be brought into compliance with DSO [Dam Safety Office] guidelines." This alone could mean substantial reconstruction.
Engineers retained by the irrigation district plan, among other things, to evaluate spillway adequacy and analyze the stability of each dam. They plan to hold a first meeting with the dam safety office sometime this month. Whether they can narrow the differences between the two sides remains to be seen. At some point, the costs of making the dams safe could become a reason to decommission them.
This debate has emerged while the separate dispute over Eightmile Lake dam rumbles on. In terms of water flow, Eightmile Lake accounts for half of the total flow from all four lakes. Combined, the other three supply the other half. What all the disputes have in common is the prospect of substantial dam repair or reconstruction, issues of access, and concerns that safety might become a pretext for increasing the footprint of dams within the Alpine Lakes Wilderness.