It may seen ironic at first glance that the U.S. Army Corps of Engineers and the U.S. Bureau of Reclamation are fasttracking a $900-million effort to address flood-risk and dam-safety issues at Folsom Dam, located near Sacramento, Calif., amid a headline-making, ongoing drought. But project officials are looking at the long term. “Local folks know that what we have is feast or famine with precipitation and the snowpack,” says Drew Lessard, area manager for the Bureau of Reclamation’s mid-Pacific region. “Yes, we have periods of drought, but it could turn over this year and go into a period of flood control for several years.” For years, both federal agencies had been making efforts to protect California’s capital, Sacramento, which lies in the crosshairs of a potential severe flood. In the mid-2000s, planning to strengthen the dam for a 200-year-storm event, the bureau considered installing a spillway plug, and the Corps considered enlarging the gates, to redirect water flows.
“For various reasons, we had challenges facing [both] of our missions,so we ended up getting together in 2005 and formulating this joint federal project,” says Lessard. “This is the first time we’ve put resources together.” With six submerged Tainter gates and an auxiliary spillway that will work in conjunction with the existing dam gates, the Joint Federal Project (JFP) addressed both missions while shaving about $500 million from the budget, Lessard estimates. The agencies shortened to 2017 the original 2021 deadline for the JFP in a commitment to Congress, says Sgt. Jeremy Nelson, a Corps quality-assurance representative.
“This is the first time the Corps partnered with another federal agency,” he says. The project reflects the ongoing reality of having to pool resources and form new partnerships to get infrastructure missions accomplished— a theme seen consistently throughout ENR’s cross-country “Low & Slow Across America’s Infrastructure” tour, which marked the JFP as its last major construction- site stop.
“Folsom is a unique facility,” says Lessard. “It’s a multipurpose reservoir. It’s not a deep canyon.” Set among rolling hills that give rise to erosion issues, the concrete gravity dam sits on the American River about 25 miles northeast of Sacramento. Built in 1955 by the Corps, the dam is 340 ft high and 1,400 ft long. Folsom Lake provides hydroelectricity and irrigation. “Folsom Lake feeds the American River, which joins the Sacramento River,” says Nelson. “Several weirs run off into farms. The closest dam from there is north of Redding—the Shasta Dam. There’s not much flood control on the way to Sacramento.”
A 1986 storm dumped 10 in. of rain on Sacramento in 11 days, which caused releases of as much as 135,000 cu ft per second of water from Folsom Dam. This flood led to a levee break in Yuba County, flooding dozens of homes (ENR 9/19/95 p. 13). In 1995, a noncatastrophic failure of a gate at Folsom Dam occurred (ENR 7/24/95 p. 9). After years of congressional fights over water bills as well as two failed Corps bids to obtain funding for a new dam, the Corps and the bureau moved ahead with environmental design plans for a new spillway and seismic repairs (ENR 5/14/07 p. 7). The federal entities collaborated with the Central Valley Flood Protection Board and the Sacramento Area Flood Control Agency (SAFCA); the bureau contributed about 35% of the funds for the JFP, covering the first two phases that the bureau also managed before handing the baton to the Corps. The Corps funded the rest, with local agenciesputting in about 35% of that cost, says SAFCA executive director Rick Johnson.
SAFCA also helped to jump-start the JFP by administering a $1-million contract that brought in consultants to help with the design—a process that might have taken up to eight months if a federal agency had sponsored it but which took only a month through SAFCA, he adds. Kiewit won a $16-million contract for the fi rst phase, which entailed excavation and construction of a 2-mile long haul road and rehabilitation of the fi lter systems for the two wing dams, says Todd Orbus, Kiewit area manager. Kiewit also held a $32-million subcontract under local fi rm Martin Brothers for the $62-million phase-two work, which entailed 2 million cu yd of excavation and two downstream cofferdams. The overall contract also included relocation of a 42-in. water supply pipeline and ancillary access roads, all completed in 2010. Granite Construction won, in 2010, a $125.9- million contract to install six bulkhead gates, each 106 tons, 24 ft wide and 39 ft high, and six 179-ton Tainter gates, each 29 ft wide at the base, with a 45-ft, 3-in. pivoting wedge.
Rubber seals in the steel embeds of each gate are grouted so tightly that “you couldn’t get a knife in between,” says Nelson. The gate system lies about 50 ft below the main dam. “Basically, you can look at it as being a drain plug in a bathtub,” says Nelson. The Tainter gates are capable of releasing up to 312,000 cu ft of water a second, enough to fi ll more than three Olympic-sized swimming pools. The control structure that houses the bulkhead and Tainter gates uses 30.6 million lb of steel.
The Corps designed the structure in-house, with the help of consultants, says Katie Charan, a Corps senior project manager for the fourth-phase new auxiliary spillway. “Most of the Tainter gates you see are operated with either chain or rope, but this is hydraulic,” she says. When the Corps awarded the contract to Granite, “we didn’t anticipate that Kiewit would come on” during the duration of that 45-month job, says Charan. When the federal agencies committed to completing the project in 2017, “we had to create [work] space for Kiewit,” she says. “It involved six or seven months of intense land negotiations. We color-coded every area and space.” The Corps also added to both contracts a stipulation requiring a dedicated project coordinator. Kiewit Infrastructure West Co. won, in 2013, the $255.1-million fourth-phase best-value contract to build the 1,100-ft approach channel and 3,027-ft spillway and stilling basin, all of which will slow down the water fl ow. The steep spillway features a series of steps, each about 2.5 ft to 3 ft high, concrete baffl e blocks at the bottom and a 10-ft pool “lip”—all intended to control the fl ow of fl oodwater and dissipate its energy.
Downstream of the control structure, Kiewit mobilized an on-site batch plant and multiple crawler cranes to install 127,000 cu yd of temperature controlled concrete for the upper chute, stepped chute and stilling basin, says Luis Paiz, Kiewit project manager. Upstream, crews built a temporary cofferdam with a secant pile cut-off wall and excavated the approach channel with blasting and rock bolting, plus installation of 15,000 cu yd of concrete, he adds.
Most of the excavation took place this year, with controlled blasts, sequenced milliseconds apart, occurring up to three times a week, says Nelson. The second pile wall consists of about 400 overlapping 3.5-ft-dia holes drilled as deep as 90 ft into granite and backfi lled with concrete. Paiz notes that, in addition to the logistical challenge of sharing staging areas with Granite, Kiewit had to schedule upstream tasks in conjunction with the seasonal fl uctuations of an active reservoir. The stepped chute reached a 40% grade, and “each step has a unique dimension,” he adds. “Blasting, excavation and rockbolting in the approach channel was in very close proximity to the existing control structure.” The fi fth phase includes a series of small contracts for landscaping, commissioning and restoration—“We blew stuff up, and now we have to restore it,” Nelson says. That restoration work includes stabilizing the right bank of the dam with rock bolts to alleviate erosion. The massive project comes at a watershed moment. “We’re in a tough time of infrastructure funding … at all levels,” Johnson explains. “We need to maximize what we can out of our existing infrastructure. Folsom is an example of that.”