Post falls dam stabilization

The stability of Washington Water Power's (WWP) Middle Channel and South Channel Dams at Post Falls, Idaho, were evaluated as required by the Federal Energy Regulatory Commission (FERC) and did not meet guideline stability criteria under Probable Maximum Flood (PMF) loading. This paper describes the stability analysis, stabilization design, design parameters, and construction of the anchors, and compares the design and as-built conditions. Value engineering was used to select the optimal stabilization measure. Constructibility, cost, and schedule were major considerations. The value engineering study evaluated 41 potential stabilization alternatives, selected post tensioning, and used scheduling criteria to optimize the design. Access considerations required the installation of five 47 strand, 7400 kN (1645k) anchors in the Middle Dam, and installation of six anchors with different capacities in the South Channel Dams.

The Washington Water Power - Black &Veatch team used value engineering, contractor prequalification, resident engineering services provided by the engineer and strong construction support provided by the Owner to successfully complete the project on a very tight schedule.