The Big Tujunga Dam, owned and operated by the Los Angeles County Department of Public Works (LACDPW), is located in the San Gabriel Mountains north of Burbank, California. The dam had been operating at 75% for over 20 years due to seismic stability concerns, and an exploration program was commissioned to determine the potential for upgrading the dam.
Since the completion of the exploration program, construction has taken place and the dam was successfully upgraded from a concrete thin-arch dam to a thick-arch dam that can withstand strong earthquakes and heavy flooding.
Los Angeles County Department of Public Works
Crux provided core drilling and sampling at a number of sloped locations along the dam. Access to these locations was particularly challenging due to surface erosion and the steep pitch of the slope. Drilling equipment was transported to boring locations by helicopter, and a specialized leveling platform system was employed. Rock bolts were installed to secure the platform in place and ensure a safe drilling environment. Crews were harnessed utilizing OSHA approved fall protection when working at these sloped locations.
Borings were drilled to depths of between 90 feet and 125 feet in subsurface materials consisting of diorite and granodiorite. All drill spoils were contained and disposed of offsite. Good quality core recovery was critical, which Crux successfully provided to the client. Crux Oriented Borehole Logging (COBL) was utilized in all borings to obtain feature orientation information, providing the client with an oriented three-dimensional view of the borehole.