Army Corps at Cottage Grove Dam

The U.S. Army Corps of Engineers Dam Safety Team is conducting a geotechnical investigation at Cottage Grove Dam, which includes boring into the dam. Cottage Grove Dam is located on the Coast Fork of the Willamette River south of Eugene, Ore. 

The work is part of a larger geotechnical assessment where data from the borings will provide information on the physical properties of the dam. The team will then use the data to study how the dam will perform under various conditions.

"We're conducting this investigation in conjunction with our routine dam safety program, which includes inspections, performance monitoring and risk assessments," said Ross Hiner, Portland District Dam Safety Program manager. "These types of investigations improve our understanding of the risk at our dams," he said. "This (drilling) activity is not going to impact the integrity of the dam."

The primary purpose of the Corps' Dam Safety Program is to maintain public safety by ensuring the dams it owns and operates are as safe as possible, and minimize risks to the public. The field work will be completed in two phases. The current phase will end February 9 and the second phase will occur in March. 

These studies are part of the Corps' Dam Safety Program, which includes periodic inspections and risk assessments, Emergency Action Plan exercises, seismic and hydrologic studies.

Construction of Cottage Grove Dam was completed in 1942, making it Portland District's second oldest dam. The U.S. Army Corps of Engineers operates 13 dam and reservoir projects in the Willamette River drainage system. Each dam contributes to a water resource management system that provides flood damage reduction, power generation, irrigation, water quality improvement, fish and wildlife habitat and recreation on the Willamette River and many of its tributaries. Since their completion, the dams have cumulatively prevented over $20 billion in flood damages to the Willamette Valley. For more information, visit


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