Wanapum Future Unit Intake Dynamic Analysis For Risk Informed Decision Making

Abstract

Grant County Public Utility District No. 2 (the District) engaged Hatch Associates Consultants Inc. (Hatch), to perform non-linear time history analysis of the Wanapum Future Unit Intakes (FUIs) using FLAC 2D as part of a risk informed review of the Wanapum Dam. The stability of the FUIs under earthquake loading relies on existing post-tensioned anchors to resist sliding and overturning.

In addition to reporting on our initial risk informed review of the FUIs, this paper presents some of the challenges faced during the analysis including how to model fully grouted anchors that cross the foundation/rock interface, account for foundation rock roughness and interface geometry, and assess post-seismic stability. The results of Hatch’s analysis are being incorporated into a prototype Risk Informed Decision Making (RIDM) process that is underway with participation of the District, FERC, and other engineering consultants.