A water pipeline that serves the city of Folsom, Calif., as well as Folsom Prison collapsed Feb. 13 at a Folsom Dam construction site, but officials were able to install a temporary bypass line with no loss or reduction of service.
The incident involved the permanent 42-in line that was being moved to make way for the second phase of a new spillway project. A temporary 24-in line was placed into service while efforts are under way to fully repair the damaged section, says Larry Hobbs, Folsom project manager for the U.S. Bureau of Reclamation, Mid-Pacific Region. “The collapse occurred while dewatering the pipeline,” says Hobbs. “No contractors were directly involved with the dewatering operation. This was being done in preparation of advance work for installing bifurcations to facilitate the permanent relocation.”
Hobbs adds that an incident investigation is being conducted to determine the cause of the pipe collapse, and will review possible technical, mechanical, modification or design flaws as well as operating procedures that may have contributed to the collapse.
Hobbs says that the emergency was handled by the bureau, city, prison, San Juan Water District and engineering contractors Abide International, Sonoma, and Syblon Reid, Folsom.
The spillway project is a Joint Federal Project with the bureau, U.S. Army Corps of Engineers, Central Valley Flood Protection Board and the Sacramento Area Flood Control Agency. When completed, the JFP will address hydrologic risks to Folsom Dam identified through the bureau�s Safety of Dams evaluation program. The JFP also achieves the Corps� objective for increasing flood protection.
The $1.6-billion project consists of a water-side approach channel, a control structure with six submerged tainter gates, a concrete-lined spillway chute approximately 3,000 ft long and a stilling basin that acts as an energy dissipation structure as discharges enter the American River below the main concrete dam.
The new auxiliary spillway also allows passage of the Probable Maximum Flood without damaging the dam.
Phase one excavation work was recently completed by Kiewit Pacific. Hobbs says that phase two is currently in the contracting process. Built in 1955, Folsom Dam is located about 25 mi northeast of Sacramento.