Corps to fill borehole test sites at Success Dam

SACRAMENTO, Calif. – The U.S. Army Corps of Engineers Sacramento District is scheduled to begin work in late April to fill and close borehole testing sites at Success Dam that were drilled to evaluate the integrity of the earthen structure and stability of soil and rock underneath the dam during the Success Dam Safety Modification Study.

From late April 2014 through late May 2014, Corps contractors will restore 78 boreholes to pre-testing conditions that are located upstream and downstream of the reservoir. All public recreation facilities around Success Lake will remain open during borehole work. A $422,041 contract was awarded March 21 for borehole closure services to Taber Consultants of West Sacramento.

A map shows the location of borehole test sites (in red) that will be filled and restored to pre-testing conditions at Success Dam near Porterville, Calif.

Contractors with the U.S. Army Corps of Engineers use a sonic drilling rig to drill borehole test sites May 2, 2006, at Success Dam near Porterville, Calif. More photos

In late 2006, the Corps began limiting the amount of water stored in Success Lake to minimize flood risk to the public while studying safety concerns at the dam. As part of the study, the Corps drilled exploratory boreholes up to 342-feet-deep, to evaluate the dam’s susceptibility to seepage and earthquakes.

On April 11 the Corps approved raising the operating restriction of the reservoir behind Success Dam to the maximum authorized storage capacity, after initial results of its baseline risk assessment showed the lake could hold more water without additional risk to the public. The baseline risk assessment is a comprehensive analysis of all the dam’s safety risks that is scheduled to be complete in summer 2014. When that is approved, the Corps will determine if any fixes are necessary for Success Dam. 

Success Dam is located on the Tule River, about five miles east and upstream of the town of Porterville. The dam and reservoir were authorized as part of the Tule River Project under the Flood Control Act of 1944 and construction was completed in 1961. The reservoir provides flood risk management, water storage and recreation benefits to the local area.