Bureau of Reclamation Plans $22.3 Million Stimulus to Stabilize Folsom Dam

By JT Long

A $22.3 million ARRA grant will push forward a contract for seismic reinforcement of Folsom Dam five years earlier than planned.

According to Larry Hobbs, Folsom Safety of Dams Project Manager, the U.S. Bureau of Reclamation plans to award at the beginning of 2010 a contract to modify piers and reinforce existing spillway gates to meet Army Corps of Engineer standards.

The bid could be released as early as October according to Rick Johnson, Corps deputy area manager.

Designs call for pier modifications, including installing struts between piers under the existing bridge deck. These bundled, high-strength steel bars will be placed vertically down the center of the piers while an external steel plate will wrap around the downstream end of the piers with supplemental tensioned anchor bars across the failure plane.

The seven 8-ft-wide reinforced concrete interior spillway piers will be reinforced with passive tie-down anchors. Each interior pier will receive five vertical passive anchors -- four upstream and one downstream passive anchor.

Plans also call for each of the eight spillway gate bays to be reinforced with horizontal steel bracing at the top of the pier walls.  

The reinforcement will reduce hydrologic (overtopping), seismic (earthquake), and static (seepage) risks, according to the bureau.

The project is part of a $926 million modification of the 50-year-old dam that includes the construction of an auxiliary spillway, control structure with six submerged tainter gates, an 1,100-ft approach channel, 3,000-ft spillway chute and a stilling basin. This will allow the dam to release water faster in case of a maximum flood event.

California’s capital city downstream of Folsom is considered to be the worst flood risk in the country.

John Baker, senior vice president and division manager for the Northern California office of Kleinfelder in Sacramento, says the project was long over due. His company worked on the engineering design of the auxiliary spillway and downstream levee improvements.

“The sooner this gets done the better; we need all the federal help we can get,” Baker said.