Dam Design and Construction

Reservoir drawdown initiated for Iron Gate Dam removal

Reservoir drawdown initiated for Iron Gate Dam removal
(Iron Gate is one of four dams on the Klamath River slated for removal)

Draining the reservoirs is the first step toward removal of the three remaining hydroelectric projects on the Klamath River, and the Klamath River Renewal Corporation (KRRC) reported it has initiated the drawdown process by opening the low-level outlet tunnel in Iron Gate Dam.

Water in the reservoirs, on the Klamath River on the California-Oregon border, will be lowered in a controlled manner through use of these tunnels at the base of the dams. Drawdown of the JC Boyle and Copco reservoirs will begin later this month, and all reservoirs are expected to be drained by the end of February, KRRC said.

Communities downstream from the dams will see changes in the river in the coming days, as sediment accumulated behind the dams is evacuated downstream. There is an estimated 17 million to 20 million cubic yards of sediment behind Iron Gate, JC Boyle and Copco No. 1, the three remaining Klamath dams slated for removal. Hydro Review reported in November 2023 that removal of Copco No. 2 dam was complete.

Together, the four comprise the Lower Klamath Hydropower Project, which occupies about 400 acres of federal land administered by the U.S. Department of Interior, Bureau of Land Management. The four developments are: J.C. Boyle Dam, a 98 MW project with an earthfill dam built in 1958; Copco No. 1 Dam, a 20 MW project with a concrete dam built in 1918; Copco No. 2 Dam, a 27 MW project with a concrete dam built in 1925; and Iron Gate Dam, an 18 MW project with an earthfill dam built in 1962.

During the initial phase of drawdown in January and February, 5 million to 7 million cubic yards of sediment is expected to go downstream. Testing by the U.S. Environmental Protection Agency and KRRC consultants determined the sediment to be non-toxic, mostly consisting of dead algae, gravels and fine clay particulates. 

“Iron Gate’s drawdown strategy is different than what people may have seen in the past with other dam removals,” said Mark Bransom, chief executive officer of KRRC. “There was no blast at this dam, instead we had the opportunity to use existing infrastructure, which allows us to precisely control the volume of water going down river, limiting downstream impacts.”

KRRC’s Aquatic Resources Working Group — which is comprised of Tribes and state and federal agencies – carefully selected the initial drawdown period. January and February are the ideal months, as there are the fewest threatened and endangered species in the mainstem and winter flows will assist with sediment evacuation. 

Water quality is expected to improve in March, after the initial phase of drawdown is complete, but it will likely take up to 24 months for water to return to usual clarity, after the establishment of vegetation in the former reservoir footprint areas. Work on deconstruction of the dams is expected to commence in May or June 2024 and be complete by fall 2024. 

KRRC is a private, independent nonprofit 501(c)(3) organization formed in 2016 by 23 signatories of the amended Klamath Hydroelectric Settlement Agreement. KRRC is part of a cooperative effort to re-establish the natural vitality of the Klamath River so that it can support all communities in the Klamath Basin. Signatories — which include the states of California and Oregon, local governments, Tribal nations, dam owner PacifiCorp, irrigators, and several conservation and fishing groups — appointed KRRC to take ownership and oversee removal of these four hydroelectric dams on the river.