November 20, 2020
Remedial work is needed on the dams at Colchuck, Klonaqua, and Square Lakes.
The Dam Safety Office of the state Department of Ecology recently did a preliminary inspection of these dams and listed all three as in poor condition. In a letter to the Icicle and Peshastin Irrigation District with an accompanying Reconnaissance Inspection Report, the dam safety office rated the dams as high hazard due to the potential damage they could cause if they failed. It did not say they are in imminent danger, but that they need substantial work and more inspections.
All three dams, as well as the dam at Eightmile Lake, were built by the irrigation district or its predecessor decades ago and are still operated by the irrigation district. All these dams are within the Alpine Lakes Wilderness in the headwaters of Icicle Creek or its tributaries. In an October 26 article entitled "State looks at repairing dams in Alpine Lakes Wilderness" the Wenatchee World incorrectly reported that the irrigation district still owns these dams and the land around them. In fact, the federal government acquired these properties after Congress created the wilderness. The Forest Service then granted easements to the irrigation district to continue operating the dams, as authorized under the Wilderness Act.
The dam safety office was prompted to inspect these dams after serious concerns arose in the spring of 2018 over the safety of Eightmile Lake dam. Those concerns were triggered by a forest fire the previous summer in the headwaters of Eightmile Lake. The irrigation district then made interim repairs while discussions continue about replacing that dam.
According to the dam safety office, its high hazard rating is based on the uncertainty of whether the emergency spillways at each dam are strong enough in the event of high water. At Klonaqua Lake, the state is also concerned about heavy seepage under the dam, which could be eroding its foundation.
Tony Jantzer, irrigation district manager, downplays any immediate danger but agrees that all three dams need work. He explained to the World that the metal outlet pipe at Colchuck Lake is rusting and should be replaced. The Klonaqua Lake dam is in the worst shape, Jantzer admits, because it is made of logs that are rotting. He proposes to replace them with baskets of rocks placed in a mesh cage. He did not discuss how these dams would be accessed for this work. At Eightmile Lake, the Forest Service required the irrigation district to ferry an excavator in by helicopter. It is understood that the state paid or reimbursed the irrigation district for that expense.
Jantzer is not sure what other repairs may be needed. The dam safety office directed the irrigation district to clear debris away from all dams and their spillways, to have professional engineers conduct stability analysis on each dam, to prepare a manual or operating plan for each dam, and to conduct annual inspections. Jantzer says the irrigation district may contest the high-hazard ratings for Klonaqua and Square Lake dams. Based on local conditions he contends they are not justified.
At all these dams, the irrigation district eventually hopes to automate outlet controls. Instead of hiking in each spring to open a valve and hiking back in every fall to close it, automated controls could be adjusted remotely by radio. So far, these new controls are only proposals.