Wanapum Dams Fracture's Influence on Rock Island Dam Fish Passage and the Associated Operational and Infrastructure Adaptations

Public Utility District No. 1 of Chelan County (Chelan PUD) implemented an Incident Command Structure (ICS) after the discovery of a crack in Wanapum Dam and subsequent emergency Wanapum Dam forebay drawdown of 26 feet on February 27, 2014.  The ICS was tasked with responding to the substantial changes to project operations at Rock Island Dam including turbine unit operations, water withdrawl for irrigators, recreation access, and adult and juvenile anadromous fish passage; all of which needed to be addressed in a short timeframe.  Through consultation with the Federal Energy Regulatory Commission and the agencies and co-managers that comprise Chelan PUD’s Rock Island Habitat Conservation Plan Coordinating Committee, an Interim Fish Passage Plan (IFPP)  was implemented to ensure safe, timely, and effective passage of juveniles and returning adults by installing three denil structures on adult ladders and modifying project spill patterns for juvenile outmigration. Forebay elevations remained within the normal operating range to avoid impacts to the juvenile spill program and maintain adult ladder exit criteria on all three adult fishways. No significant fish passage delays were observed at Rock Island Dam while the Wanapum Reservoir was drawn down.