News Release
| Release Number: | 02-109 |
| Dated: | 6/26/2002 |
| Contact: | Heidi Y. Helwig, 503-808-4510 |
Portland, Ore.- Water quality and sediment samples taken from within and around Cougar Reservoir on the McKenzie River indicate there are no unsafe levels of contaminants in the water, and only one contaminant of concern was found in the sediment, the U.S. Army Corps of Engineers announced today.
Water quality samples taken from below, above and within the reservoir, and five sediment samples taken from the lakebed surrounding the reservoir, were screened for more than 70 different chemicals, including heavy metals, pesticides, PAHs (polynuclear aromatic hydrocarbons), PCBs and herbicides. Out of all the results, only low levels of dichlorodiphenyltrichloroethane (DDT) were found in the sediment.
The levels of total DDT, a once-common pesticide, range from 5.32 parts per billion (ppb) to 32.63 ppb, said Corps biologist Tim Sherman. These levels fall well below the red-flag level of 2,000 parts per billion, which is considered unsafe for residential areas, and below 50 ppb, the level at which current guidance requires additional testing to determine the risk of the build up of the toxin over time in the food chain, known as bioaccumulation, Sherman said.
The levels of contamination detected in four of the five sediment samples, however, did exceed 6.9 ppb, the maximum amount of DDT allowed for in-water disposal under Clean Water Act guidelines, said Sherman. Though the Corps is not dredging, it has elected to apply the dredging sediment quality guidelines as a basis of determining what degree of risk, if any, the low levels of DDT may pose to the environment. The exposed lakebed sediment will ultimately come in contact with water as the reservoir is refilled during winter flood damage reduction operations, Sherman said. Though some DDT in the lakebed will be exposed to the water, it will remain bound to the sediment, he said.
"Although first round tests indicate a relatively low risk to the environment, we want to err on the side of caution. Additional testing will be conducted to fully characterize the risk," said George Miller, project manager for the Willamette River Temperature Control Project. "Our next step is to coordinate with the appropriate regulatory agencies, determine additional testing requirements, and assess the levels of risk."
The Corps is coordinating with the Environmental Protection Agency, U.S. Forest Service, National Marine Fisheries Service, U.S. Fish and Wildlife Service, Oregon State Department of Health, Oregon Department of Environmental Quality, and Oregon Department of Fish and Wildlife, to set up a program to monitor these levels, Miller said.
The Corps began drawing down Cougar Reservoir on April 1 to allow for construction of a multi-level intake tower. Sediment samples taken before the drawdown did not reveal the presence of significant levels of toxic chemicals, including DDT-a pesticide commonly used on crops, in forests and for mosquito control before its use was banned in 1972, Miller said. Also, water quality samples taken in May when the water was most turbid from the reservoir drawdown did not reveal any contaminants.
Therefore, the Corps believes the erosion that occurred as a result of the drawdown brought decades-old sediment to the surface of the lakebed. In addition, the presence of two other chemicals--DDE and DDD-which are biodegradation products of DDT, indicate the DDT has been present in the sediment for some time. Cougar dam was completed in 1963.
The tower now under construction will allow the Corps to draw water from differing depths in the reservoir, mixing it to the optimum water temperature for release below the dam to more closely match natural conditions needed by fish. The changes will improve river conditions for salmon and resident fish in the South Fork McKenzie and McKenzie rivers.