The largest dam removal project in U.S. history is set to begin in 2020 on the Klamath River in Siskiyou County, according to documents filed recently with federal regulators.

The Klamath River Renewal Corp. plans to begin site work in two years to remove four dams on the Klamath River and deconstructing the dams will begin in 2021, according to the "Definite Plan for the Lower Klamath Project."

“We have completed a major milestone through the development and filing of this plan,” coporation Executive Director Mark Bransom said in a news release. “KRRC has developed this plan with tremendous respect for the complexity of the project and with extraordinary care in its efforts to enhance benefits and minimize impacts to local communities.”

Under the proposal submitted to the Federal Energy Regulatory Commission last week, the corporation plans to remove four dams: J.C. Boyle, Copco No. 1, Copco No. 2 and Iron Gate. Three of the dams are in Siskiyou County and one, the J.C. Boyle Dam, is in Southern Oregon.

This map shows the locations of the four dams that would be removed on the Klamath River.(Photo: Klamath River Renewal Corp.)

FERC and a separate independent board of consultants still has to approve the plans.

The corporation says removing the dams will improve water quality, revive fisheries in the river, create local jobs, boost tourism and recreation.

The dam removal will cost just under $400 million, according to the 2,300-page definite plan. The report is available online at www.klamathrenewal.org/definite-plan/.

The plan outlines the process of drawing down the reservoirs, disassembling the dams and restoring and replanting with vegetation the former areas that were inundated by the dams.

While the corporation promotes the benefits of removing the dams, several local groups in Siskiyou County and in Southern Oregon have opposed removing the dams because of possible harm to local economies and to the environment.

The Siskiyou County Board of Supervisors has formally come out against the proposal. Ironically, the board cited the potential for negative economic and environmental effects of removing the dams.

In a 2017 letter to the State Water Resources Control Board, Siskiyou County supervisors said the effects of releasing 20 million to 30 million cubic yards of sediment from behind the dams has not been adequately evaluated.

"Other issues include the potential for catastrophic floods, either during dam removal activities, or thereafter; and property value loss in the areas around Iron Gate and Copco Dams, which Siskiyou County estimates would be several million dollars," the letter says.

However, PacifiCorp, which owns the dams, has signed off on the plan to remove the dams. The definite plan is one step in a process to transfer ownership of the FERC-issued licenses to operate the dams from PacifiCorp to the corporation.