US Army Corps of Engineers
Portland District

Corps confirms localized sediment contamination in Big Cliff Reservoir. Read news release here

Willamette Valley Environmental Compliance

Portland District operates 13 dams in the Willamette River Basin. The dams, authorized by the Flood Control Act of 1936, contribute to a water resource management system that provides flood risk management, power generation, water quality improvement, irrigation, fish and wildlife habitat and recreation on the Willamette River and many of its tributaries.

The Corps found disposal sites at various dams within the valley that were from original construction and operations in the early 1950s. The Corps has a responsibility to clean up disposal sites from dam construction, as construction and disposal regulations and procedures were very different back then. 

Small site cleanups & the Environmental Compliance Program

In 1990, the Corps initiated an environmental compliance program using regulations governing environmental compliance at the time and Engineering Regulation 200-2-3. Under the environmental compliance program, the Corps completed District Environmental Response Team (DERT) investigations for potential contaminants throughout the Willamette Valley. In addition, the DERT conducted small site cleanups:

1990

The Corps initiated an environmental compliance program.

1992-1997

Corps conducted sampling, excavation and clean up at Fall Creek, Cougar, Green Peter, Lookout Point, Detroit and Foster dams.

2010

Order for USACE Civil-Works sites to begin legacy contamination reviews.

2012

Portland District conducted a Legacy Contamination Assessment throughout the Willamette Valley to review findings of previous investigations and consider subsequent corrective actions.

Big Cliff remediation

Due to a wire-rope failure in 2009, the Corps conducted an emergency drawdown of Big Cliff Reservoir. During this drawdown, staff identified construction debris and contamination. The Corps sampled reservoir sediment, which indicated the presence of hazardous metals and solvents; however, the levels of contamination did not require urgent cleanup actions (according to EPA guidelines). It did trigger actions to further investigate the area, which have been ongoing.


 

Timeline of events:

2009

The Corps identified construction debris and contamination in Big Cliff Reservoir.

2010

A Detroit Dam powerhouse fire lead to a placement on the Federal Agency Hazardous Waste Compliance Docket. This placement required the Corps to perform a Preliminary Assessment under the Comprehensive Environmental Response, Compensation and Liability Act (CERCLA).

2010

Order for USACE Civil-Works sites to begin legacy contamination reviews.

2012

Portland District conducted a Legacy Contamination Assessment throughout the Willamette Valley to review findings of previous investigations and consider subsequent corrective actions.

2014

Corps completed a Preliminary Assessment with results indicating that no immediate response to the contamination was needed but a more detailed Site Inspection is warranted at Big Cliff Reservoir and Dam area.

The area of localized sediment contamination at Big Cliff at low pool elevation.
2015

Corps completed the Site Inspection and officially notified EPA of the results of preliminary assessment/site investigation (PA/SI) as required.

2016

Corps took water samples upstream and downstream of the former work area. With the exception of Arsenic, which was detected in similar levels in both upstream and downstream samples, results did not exceed Oregon State and EPA screening levels. 

2017

Corps collected sediment samples as part of a Remedial Investigation to determine the nature and extent of any contaminants in the immediate area.  

2018
Corps collected additional water samples during low flow conditions. However, results indicated there was no risk from exposure to contaminants in the water.
 
2019
Corps finalizes Remedial Investigation report and informed the public of the findings.