Annual Deformation Monitoring & Sediment Cross Section Surveys

Client—Lewis County PUD

Located in Lewis County, the Cowlitz Falls Dam is a 70 megawatt hydroelectric dam that was constructed in the early 1990’s. At the time of construction, Gibbs & Olson provided quality control checks, reviewed all baseline and control monuments for the purpose of validating and regulating all staking for the construction project. Verification of construction staking by Gibbs & Olson allowed the design engineers to focus on critical layout elements of the dam such as sluice gates, generator placement, and on-going dam positioning monitoring. In addition, Gibbs & Olson provided off-site design and construction support survey services for related projects such as recreational and boat launch facilities.

Gibbs & Olson has an ongoing contract with the PUD since the dam was initially constructed. Under our contract, we perform annual deformation monitoring and cross section surveys. The deformation monitoring surveys are performed across the 739 foot dam width and include 12 monument points along the face of the dam. Data collected from the deformation monitoring is submitted to the PUD for completion of their required reporting to the Federal Energy Regulatory Commission. The cross section surveys are performed at 12 locations along a 14 mile stretch of the Cowlitz River starting at the dam and continuing upstream to Randle, Washington. The PUD uses the cross section data  to monitor sediment build up along the 14 mile stretch of river.