Water levels at Big Cliff Reservoir will be lower October 13-27 to allow the U.S. Army Corps of Engineers to conduct sediment sampling, USACE’s Portland District said in their latest release.
USACE is collecting the sediment samples as part of a Remedial Investigation to determine the nature and extent of any contaminants in the immediate area.
Since the initial discovery of construction debris, USACE has identified that contaminants of concern are present in the sediment; however, samples of surface water, collected last year, found no exceedances of risk-based screening levels indicating that there are no risks to downstream communities and water users.
“We are proceeding with a more comprehensive investigation in order to understand the nature and extent of contaminants in the sediment. The results will be used to determine if further actions, including clean up, are warranted,” said Mark Dasso, Portland District project manager.
“We’ve been very methodical about our process of collecting and analyzing information to better understand the site. This round of sampling will focus on sediments in the area.”
The water drawdown started on October 13 and reached approximately 1175 feet by today. This is about 27 feet lower than typical low levels at Big Cliff.
USACE’s regulators will further lower the reservoir to 1167 feet for continued sampling before increasing back to 1175 feet until October 27.