Hume Lake Dam

Challenges

Hume Lake Dam, constructed in 1908, is the world’s first multi-arch, reinforced concrete dam.  The dam was designed by John Eastwood and consists of 12 arched bays, each 50 feet in diameter with a maximum height of 50 feet.  Located east of Fresno, California in the Sequoia National Forest, the structure was originally used as a log pond and water source for a 17-mile flume to transport timber downstream.  

The dam has undergone several rehabilitations throughout its life cycle, with the most recent occurring in 2016 to install a waterproof membrane, necessary grouting, and a corrosion protection system on the outlet works.  Additional engineering is needed to evaluate the static and dynamic structural stability of the dam to ensure its compliance with guidelines from the Federal Emergency Management Agency. 

Solution

RJH, in collaboration with the Natural Resources Conservation Service and the U.S. Forest Service (USFS), performed a comprehensive review of existing information, including previous investigation reports, seismic analyses, and material testing results. Concrete core samples were obtained from the 2016 rehabilitation and are being tested by petrographic analyses, compressive strength tests, and others to support the structural stability analyses. A site visit was conducted to identify any possible constraints to the rehabilitation, and a summary report was delivered to the USFS to document findings of the data review.  

A three-dimensional finite model was developed to evaluate the dam’s capacity to withstand the site-specified maximum credible earthquake and the probabilistic 5,000-year earthquake event.  The risk of catastrophic failure and severe damage was evaluated, and the results were provided in a structural evaluation report delivered to the USFS.  RJH delivered recommendations for additional studies and, if the structural capacity is deemed inadequate, RJH will develop rehabilitation concepts.