Continuity of Risk Informed Decision Making from Design Through Construction for the Isabella Lake Dam Safety Project

摘要

Dam Safety modifications to the Isabella Auxiliary Dam are currently under construction to address actionable potential failure modes. Isabella Lake is located on the Kern River 34 miles upstream of the City of Bakersfield in Kern County, California. Isabella Dam has been designated as a Dam Safety Action Class (DSAC) I project by the U.S. Army Corps of Engineers (USACE), requiring action to reduce probabilities of failure and associated consequences. Isabella Dam construction began in 1948 and was completed in 1953, and consists of two embankment dams that provide flood control, water supply, power generation and recreation benefits to the region. The modifications under construction are addressing actionable potential failure modes identified over three primary areas of deficiency, including hydrologic overtopping, internal erosion of the foundation and seismic instability from strong ground motion/fault rupture. This paper includes a summary of the potential risk and dam safety modifications under construction. This paper focuses on the importance and challenges of maintaining focus on Potential Failure Modes (PFM's) and risk informed decision making through design and in to construction. The paper also discusses the approach to maintain continuity as the project transitioned between the Dam Safety Modification Study (DSMS), Preconstruction Engineering and Design (PED), and construction/implementation for successful completion of the Post Implementation Evaluation (PIE).