McGuire Dam Following the Raise
Cornforth Consultants, Inc. were the lead geotechnical designers for a 30-foot raise of an existing 80-foot high water supply embankment dam located in the Oregon Coast Range. Design tasks included subsurface exploration, embankment static and seismic stability, a grout curtain for seepage control, settlement estimates, rock slope stability and rock bolt reinforcement for a 220-foot tall excavation for a new spillway entrance, spillway foundation recommendations, and developing material borrow sources for earth and rock fill.
Liquefaction analyses determined that an upstream random fill section could liquefy during the design-level earthquake. Several remedial options were evaluated to improve the resistance to liquefaction. These options included in-situ grouting, stone columns, and partial excavation of the random fill. An evaluation of costs and construction sequencing resulted in selection of partial excavation for remediation. Additional tasks included preparation of contract drawings and technical specifications for the construction bid package, and providing on-site monitoring during construction.