Tacoma Power's Cushman Dam No. 1 was completed in 1926. It is a single curvature arch dam, with a maximum height of 80 m. Working with FERC Part 12 consultants, Hatch Energy carried out non-linear static and dynamic analysis of the dam, using the 3DEC program. 3DEC was chosen because of its ability to model the behavior of joints in the dam, allowing for slip. The analysis revealed that some slippage would take place in an extreme seismic event, but the structure was still sound. Cushman Dam No. 2 will be analyzed in the same way.