AJ Diani Construction Co of Santa Maria, California, was awarded a US$4M contract for the work on 30 September 2005. The company is expected to begin assembling equipment at the work site in late November.

The modification features sand and gravel layers that will be installed within the downstream portion of the dam. These layers will prevent movement of the clay core materials during an earthquake as well as provide a means to collect and channel any seepage.

The modifications are expected to take 10 months to complete.