Folsom Dam Auxiliary Spillway Control Structure will be approximately 140 foot tall and consist of six gates which will improve the ability to manage large flood events by allowing more water to be safely released earlier in a storm event and leaving more storage capacity in the reservoir to hold back the peak inflow when it arrives. With a peak inflow of 450,000 cubic feet per second in a 200-year design storm, releases can be held to 160,000 cubic feet per second or less, which can be safely conveyed with the improved American River levees. The new auxiliary spillway also allows passage of the probable Maximum Flood (PMF) without damaging Folsom dam.
ENGEO is currently installing geotechnical instrumentation for the Control Structure. Instrumentation for the project includes: multi-point borehole extensometers, piezometers, inclinometers, load cells, joint meters, strong motion accelerographs, as well as an automated data acquisition system. Generally, the instruments use vibrating wire technology to communicate measurements to data loggers which can be read in real time as a part of the control structure operations.