Screening-Level Evaluation of Contaminants in Sediments from Three Reservoirs and the Estuary of the Klamath River, 2009-2011

The purpose of this report is to inform the Department of Interior Secretarial Determination process regarding the potential for adverse ecological or human health effects from chemical contamination in Klamath Reservoir sediments. It evaluates if the dams are removed and a portion of the accumulated sediments is flushed downstream (Proposed Action or “dams removed”) or if the dams remain in place (No Action or “dams in”). The report does not include an evaluation of the physical effects associated with the Proposed Action. This report is only intended to provide a screening-level evaluation to inform the Secretarial Determination. A stepwise process based on the Sediment Evaluation Framework (SEF) was applied that evaluated sediment and elutriate chemistry, laboratory bioassays, bioaccumulation studies, and tissue of fish from the reservoirs. This process generated multiple lines of evidence that were compared to five relevant exposure pathways of biota and human receptors to identify potential adverse effects. The results of this evaluation suggest the Klamath Reservoir sediments can be considered relatively clean, with no chemicals present at levels that would preclude their release into downstream or marine environments. Accordingly Klamath Reservoir sediments are expected to pose no adverse effects, limited effects, or minor effects under the five exposure pathways under the Proposed Action and No Action alternatives. In the future, if there is an affirmative decision, efforts would begin to develop detailed plans for dam removal and permitting processes.