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 Fears
“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.”
1986台风10。我的雨在萨克拉门托n 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.
第四阶段新辅助溢洪道的军团高级项目经理凯蒂·查兰（Katie Charan）表示，在顾问的帮助下，该军团在内部设计了该结构。她说：“您看到的大多数tainter大门都是用链条或绳子操作的，但这是液压的。”Charan说，当军团将合同授予花岗岩时，“我们没想到Kiewit会在45个月的工作期间”。她说，当联邦机构致力于在2017年完成该项目时，“我们必须为Kiewit创建[工作]空间。”“这涉及六到七个月的激烈土地谈判。我们对每个区域和空间进行了颜色编码。”军团还增加了两项合同，要求专门的项目协调员。Kiewit基础设施West Co.于2013年获奖，这是建立1,100英尺的进近渠道和3,027英尺的溢洪道和Stilling盆地的2.555亿美元的最佳价值合同，所有这些合同都将减慢水上的速度。陡峭的溢洪道具有一系列台阶，每个台阶在底部约2.5英尺至3英尺高，混凝土baffl e块和一个10英尺英尺的池“唇” - 所有旨在控制Fl Oodwater的Fl OW并散发其能量。
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.
尼尔森说，大部分发掘都是在今年进行的，并进行了受控的爆炸，对毫秒隔开了毫秒，每周最多发生三次。第二个桩壁由大约400个重叠的3.5英尺二木孔组成，深度为90英尺，直至花岗岩，并用混凝土钻出。Paiz指出，除了与花岗岩共享分期阶段区域的后勤挑战外，Kiewit还必须将上游任务与活动储层的季节性无关系一起安排上游任务。他补充说，阶梯滑道的成绩达到40％，“每个步骤都有一个独特的维度。”“进近通道中的爆破，挖掘和摇摆非常接近现有的控制结构。”FI FTH阶段包括一系列用于美化，调试和修复的小合同 - “我们炸毁了东西，现在我们必须恢复它，”尼尔森说。修复工作包括用岩石螺栓稳定大坝的右岸以减轻侵蚀。大型项目是在一个分水岭的时刻。约翰逊解释说：“我们正处于基础设施资助的艰难时期……在各个层面上。”“我们需要最大限度地利用现有基础架构中的一切。 Folsom is an example of that.”
