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San Luis Unit Project
Non-interactive picture of the BF Sisk Dam aka San Luis Dam
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West San Joaquin Division - San Luis Unit Project History (69 KB) (pdf)
General Description| Development| Benefits

General Description

The San Luis Unit, a part of the Central Valley Project and also part of the State of California Water Plan, was authorized in 1960. Reclamation and the State of California constructed and operates this unit jointly. Some features are `joint-use facilities` of the Federal Government and the State. The principal purpose of the Federal portion of the facilities is to furnish approximately 1.25 million acre-feet of water as a supplemental irrigation supply to some 600,000 acres located in the western portion of Fresno, Kings, and Merced Counties.

The major portion of the San Luis Unit is a combined effort of the Federal and State governments; 55 percent of the total cost is contributed by the State of California and the remaining 45 percent by the United States. The joint-use facilities are O`Neill Dam and Forebay, B.F. Sisk San Luis Dam, San Luis Reservoir, William R. Gianelli Pumping-Generating Plant, Dos Amigos Pumping Plant, Los Banos and Little Panoche Reservoirs, and San Luis Canal from O`Neill Forebay to Kettleman City, together with the necessary switchyard facilities.

The Federal-only portion of the San Luis Unit includes the O`Neill Pumping Plant and Intake Canal, Coalinga Canal, Pleasant Valley Pumping Plant, and the San Luis Drain.

San Luis Reservoir serves as the major storage reservoir and O`Neill Forebay acts as an equalizing basin for the upper stage dual-purpose pumping-generating plant. Pumps located at the base of O`Neill Dam take water from the Delta-Mendota Canal through an intake channel (a Federal feature) and discharge it into the O`Neill Forebay. The California Aqueduct (a State feature) flows directly into O`Neill Forebay. The pumping-generating units lift the water from the O`Neill Forebay and discharge it into the main reservoir. When not pumping, these units generate electric power by reversing flow through the turbines. Water for irrigation is released into the San Luis Canal and flows by gravity to Dos Amigos Pumping Plant where it is lifted more than 100 feet to permit gravity flow to its terminus at Kettleman City. A State canal system continues to southern coastal areas. During irrigation months, water from the California Aqueduct flows through the O`Neill Forebay into the San Luis Canal instead of being pumped into the San Luis Reservoir. Two detention reservoirs, Los Banos  and Little Panoche control cross drainage along the San Luis Canal. The reservoirs also provide recreation and flood control benefits.

Plans to build the San Luis Drain to dispose of agricultural drainage on the west side of the San Joaquin Valley did not materialize, allowing the drainage to accumulate at Kesterson Reservoir.


B.F. Sisk Dam and Reservoir

These joint Federal/State facilities are located on San Luis Creek near Los Banos, California. Completed in 1967 and dedicated on April 20 of that year, B. F. Sisk Dam is a zoned earthfill structure 382 feet high with a crest length of 18,600 feet; it contains 77,656,000 cubic yards of material. The dam`s crest is 30 feet thick; the maximum base width is 2,420 feet. In the United States, only the U.S. Army Corps of Engineers` Fort Peck and Oahe Dams along the Missouri River Basin carry greater mass.

Five layers, or zones, of material make up the B. F. Sisk Dam. The core of the embankment, Zone 1, consists of 41 million yards of clay, silt, sand, and gravel. Twelve passes by tamping rollers compacted the conglomeration into six inch layers. Zone 2 comprises sand, gravel, and cobbles compacted to 12-inch layers. Shale, sandstone, conglomerate fragments, clay, silt, sand, and gravel tamped by rollers into 12-inch layers form Zone 3. Zone 4 is made up of rock fragments ranging between 3/16 inch and 8 inches compacted by a crawler-type tractor in 12-inch layers. The outside surface, Zone 5, is more than 3 million cubic yards of rock fragments ranging from 8 to 36 inches, taken from nearby Basalt Hill. Work on San Luis Dam concluded two months ahead of schedule, in August, 1967.

The reservoir has a capacity of 2,041,000 acre-feet and is used to store surplus water of the Sacramento-San Joaquin Delta. Releases are made through the San Luis Pumping-Generating Plant, using its power generating capacity. The lake filled for the first time on May 31, 1969. The reservoir offers facilities for fishing, boating, water skiing, and camping.

B. F. Sisk Dam is near two seismic faults. It is twenty-eight miles from the San Andreas Rift, and 23 miles from the Calaveras-Hayward Faults. Designed to withstand the effects of an earthquake comparable to the one that leveled San Francisco in 1906, the dam`s core material is resistant to progressive erosion and its appurtenant structures were built on a firm rock foundation.

A hydraulic junction point for both Federal and State waters, the B. F. Sisk Reservoir serves as a forebay for the Gianelli Pumping-Generating Plant. The dam`s spillway incorporates an ungated morning-glory hole, shaft, conduit, chute, stilling basin, and riprap-lined channel. The spillway functions as a safety device to release any excess storage. Excess is a consequence of flooding when the reservoir is at normal water surface elevation or continued pumping after the reservoir fills. The entire inflow design flood of 24,500 acre-feet can be stored in two feet of excess reserve in the reservoir.

After a reservoir drawdown in 1981, 400,000 cubic yards of embankment slid down 177 feet along a 1,100 foot section near the crest of the dam. On September 15, a State maintenance crew first discovered movement on a hill butted against the dam. Three days later, rocks and dirt continued to creep down the dam`s face.   Reclamation`s Mid-Pacific Regional Director at that time, Mike Catino, described the potential of a disaster at San Luis as `a one in five chance of happening.` Repairs, completed in August 1982, required 1.4 million cubic yards of select material to stabilize the embankment. Reclamation moved quickly, and `not one acre-foot of water was lost to the farmers.` On July 30, 1984, a crack opened along the embankment, parallel to the dam`s centerline, but it eventually stopped of its own accord. No other movement or cracks have been reported at the dam since 1984.

O`Neill Dam and Forebay

These joint Federal/State facilities are located on San Luis Creek, 2.5 miles downstream from San Luis Dam. O`Neill Dam, completed in 1967, is a zoned earthfill structure with a height of 87 feet and a crest length of 14,300 feet. It contains 2.8 million cubic yards of material, the dam was completed in 1967. The top 20,000 acre-feet act as re-regulator storage necessary to permit offpeak pumping and onpeak generation by the main San Luis Pumping-Generating Plant.

The O`Neill Forebay Inlet Channel extends 2,200 feet from the Delta-Mendota Canal to deliver water to the O`Neill Forebay. The forebay holds 56,000 acre-feet, part of which is used for regulator storage to permit off-peak pumping and on-peak generation. Six pumping units of the O`Neill Pumping-Generating Plant lift water 45 to 53 feet into the forebay. The forebay, with a capacity of 56,400 acre-feet, is used as a hydraulic junction point for Federal and State waters. Recreation facilities  included at the forebay for picnicking, camping, swimming, boating, water skiing, and fishing.

O`Neill Pumping Plant

This Federal facility consists of an intake channel leading off the Delta-Mendota Canal, 70 miles from the Tracy Pumping Plant, and six pumping-generating units. The plant was under construction from 1964 to 1967. These units operate as pumps to lift water from 45 to 53 feet into the O`Neill Forebay. When water is occasionally released from the forebay to the Delta-Mendota Canal, these units operate as generators. When operating as pumps and motors, each unit can discharge 700 cubic feet per second (cfs) and has a rating of 6,000 horsepower. When operating as turbines and generators, each unit has a generating capacity of about 4,200 kilowatts.

William R. Giannelli Pumping-Generating Plant

This joint Federal/State facility, located flush against the San Luis Dam, lifts water by pump-turbines from the O`Neill Forebay into San Luis Reservoir. During the irrigation season, water is released from San Luis Reservoir back through the pump-turbines to the forebay, and energy is reclaimed. Each of the eight pumping-generating units uses 63,000 horsepower when puumping or will develop 53000 kilowatts when generating. As a pumping station to fill San Luis Reservoir, each unit lifts 1,375 cfs at 290 feet total head. As a generating plant, each unit passes 1,640 cfs at the same head. It became California`s largest hydroelectric plant at its completion in 1967.

San Luis Canal

This joint Federal/State facility is a concrete-lined canal with a capacity ranging from 8,350 to 13,100 cfs. Public access sites are provided for fishing. The San Luis Canal is the biggest earth-moving project in Reclamation history. It is the federally-built and operated section of the California Aqueduct and extends 102.5 miles from the O`Neill Forebay, near Los Banos, in a southeasterly direction to a point west of Kettleman City.

The 138-foot-wide channel is 36 feet deep, 40 feet wide at the bottom, and lined with concrete. Before computers were available, field surveyors and engineers spent the better part of a day converting a mile`s worth of raw field data into working cross-sections and engineering material. Keypunch cards and magnetic tape fed into a Reclamation computer in Denver cut the calculating time for San Luis Canal by an estimated 26.6 man-years.

The first release of water from the O`Neill Forebay to the initial reach of the canal was on April 13, 1967. Water was pumped from Dos Amigos Pumping Plant into the second reach in October of that year, and by December, water reached Kettleman City at the end of Reclamation's canal. At that point, the conduit becomes the State`s California Aqueduct.

Dos Amigos Pumping Plant

This joint Federal/State facility, 17 miles south of the Forebay, is a relift plant in the San Luis Canal. The plant contains six pumping units, each capable of delivering 2,200 cfs at 125 feet of head.

Pleasant Valley Pumping Plant

Pleasant Valley Pumping plant is a Reclamation facility which pumps water into the Coalinga Canal. Westlands Water District operates and maintains this pumping plant . This Federal facility lifts water 180 feet from an intake channel leading from the San Luis Canal at mile 74. Three 7,000-, three 3,500-, and three 1,250-horsepower units are used to deliver 1,135 cubic feet of water per second to the Coalinga Canal and 50 cubic feet of water per second to a distribution lateral serving adjacent lands north of the pumping plant.

Coalinga Canal

This Federal facility, formerly called Pleasant Valley Canal, carries water from the turnout structure on the San Luis Canal to the Coalinga area, in Fresno County. The system includes a 1.6-mile intake channel to the Pleasant Valley Pumping Plant and 11.6 miles of canal. The initial capacity of the canal is 1,100 cfs, decreasing to 425 cfs at the terminus. Reaches 1 and 2 of the canal are operated by the Westlands Water District (WWD).

Los Banos and Little Panoche Detention Dams and Reservoirs

Los Banos and Little Panoche Detention Dams are southwest of the town of Los Banos on Los Banos and Little Panoche Creeks. These joint Federal/State facilities are required to protect the San Luis Canal by controlling flows of streams crossing the canal. Los Banos Reservoir (http://www.recreation.gov/detail.cfm?ID=23) has a capacity of 34,600 acre-feet. It protects the city of Los Banos and adjacent areas from damaging floods and provides recreation facilities for picnicking, camping, swimming, fishing, and boating.

Little Panoche Reservoir (http://www.recreation.gov/detail.cfm?ID=22) detains floodwater collected over 81.3 square miles of mountainous drainage area and provides limited recreation facilities. Both are zoned earthfill detention dams. Los Banos Detention Dam, completed in 1965, is 167 feet high with a 1,370-foot-long crest. It provides 34,500 acre-feet of flood control capacity with a maximum controlled release of 1,000 cfs.

Little Panoche Detention Dam, completed in 1966, contains a little more than a million yards of earthfill in its 151-foot-high embankment. The dam`s crest is 1,440 feet long and 30 feet wide. The reservoir`s capacity is 5,580 acre-feet.

San Luis Drain and Kesterson Reservoir

The San Luis Drain, a Federal facility, is designed to convey and dispose of subsurface irrigation return flows from the San Luis service area. Construction began in April 1968. The drain was designed to collect subsurface drainage from 8,000 acres in the San Luis service area, and transport the water for disposal in the west Delta. The design capacity was 300 cfs.

Of the planned 188 miles of drain, 87 miles were completed; construction was halted in 1975 because of mounting costs and concerns about the quality of the agricultural drainage that would go into the Delta.

The concrete lined canal ran from the town of Five Points to a series of twelve shallow ponds formed by earthen dikes. Kesterson Reservoir is a collection of ponds outside the town of Gustine, in Merced County, where water was ponded, regulated, and allowed to evaporate pending approval and construction of an outlet for the San Luis Drain. The reservoir served in the conservation and management of wildlife and recreation and was designated as a national wildlife refuge.

Distribution System

Reclamation is constructing a system of laterals and relift pumping facilities to take water from the San Luis Canal and convey it to over 583,000 irrigable acres. Is the distribution system complete? Could we get specifications (how many miles of laterals, what kind of relift pumping plants, etc.)

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The introduction of the first motorized pump to the San Joaquin Valley brought with it an agricultural revolution. Pumping California`s underground warter saved many owners of overgrazed ranch land. Within two decades, this new form of irrigation drastically changed local agriculture, providing an impetus for fruit, nut, and cotton production as grazing and grain production slowly fell out of favor. In 1922, 33,000 acres were irrigated directly from pumping. Despite the hard times brought by the depression, by the end of the 1930s, approximately 90,000 acres received water from underground. The growers` increasing dependency on pumping led to a ten foot per year drop in the underground water table, and wells were drilled as deep as 2,000 feet beneath the surface.

America`s entry into World War II placed additional stress on the water table, as the national demand for cotton, flax, wheat, and vegetables expanded. In 1942, the modern era of Westside water development began. That year, landowners in western Fresno and Kings Counties formed the Westside Landowners Association. According to a 1945 Department of Agriculture report, a select few each owned over 1,000 acres in the San Joaquin Valley. These owners sought Reclamation`s help in drawing Central Valley Project surface water to the west side of the valley. In 1945, Reclamation prepared a plan detailing the multiple-purpose development of the water resources of the entire Central Valley. The report noted the rapid growth of agriculture on the west side of the San Joaquin Valley and the need for importation of a new water supply. Unfortunately, much of the CVP`s progress had been halted by a Federal order suspending completion of nonessential projects.

As long as the problem of over-pumping remained unseen and underground, it did not weigh heavily on the minds of most in the valley. But, by the early 1950s, overdraft on the aquifer was up to 500,000 acre-feet per year and a solution had to come quickly. In addition to headaches brought by a draining aquifer, studies found that the sodium content of the local groundwater ranged between 20 percent and more than 90 percent. In 1952, as overdraft problems worsened and the quality of groundwater declined, farmers on the west side formed the WWD. A 1954 Federal investigation recommended construction of a storage facility. Reclamation favored a site along the Pacheco Pass Highway encircled by the eastern foothills of the Diablo Mountains. Reclamation believed this spot would make an excellent location for a gigantic reservoir.

In December 1955, Reclamation submitted the San Luis Unit feasibility report to the State of California. In March of the following year, the State offered its recommendations on the report. California conceived their own venture, the Feather River Project at Oroville. Feather River would store water to flow down the Sacramento River where the State would transfer it southward by canal. With passage by the State legislature of the Burns-Porter Act of 1959, authorizing the State Water Projects' initial facilities, it was apparent the State needed off-stream reservoir capacity to supply the WWD acreage already in production. California took the unusual step of offering to work with the Federal government to design a much grander facility along Los Banos Creek.

The State Director of Water Resources lobbied Washington for a State/Federal partnership. Through persistence, the unusual notion of a Federal/State partnership gained increasing acceptance during Federal congressional hearings in 1956, 1958, and 1959. On May 16, 1960, Reclamation and the State of California entered into an agreement for coordinated operation of the Federal Central Valley Project and the State Water Facilities, later known as the California Aqueduct. A first in Federal-State relations, the contract agreed to construction of `joint-use facilities,` and a 55-45 spilt of costs between the State of California and the Federal Government. The San Luis authorizing act (Public Law 86-488, 86th Congress) was signed into law by the President on June 3, 1960. In November, California`s voters agreed to a $1.75 billion general obligation bond issue to begin building the Project`s dams, pumping plants, and aqueducts. The State Water Project, like the CVP, takes surplus water from northern California streams and redirects it toward the south. Now in partnership with the State, Reclamation increased the reservoir`s design capacity to twice the size originally contemplated. The State okayed the San Luis Agreement on December 29, 1961. The Secretary of the Interior signed for the Federal Government the following day.

By the mid-1990s, all WWD acreage holders had agreed to abide by the provisions of the Reclamation Reform Act (RRA) of 1982. Water pricing in the wake of RRA has changed for all CVP water users, but within Westlands, the cost of water varies on category of service. In 1988, six years after the enactment of RRA, water cost WWD users $42.03 per acre-foot including capital, operation and maintenance and interest. That same year, there were 584 WWD water users spread over a total irrigable acreage of 528,718, averaging 905 acres per user.

The San Luis authorizing act (Public Law 86-488, 86th Congress) was signed on June 3,1960.
Recent Developments - Kesterson

Kesterson`s runoff contained high levels of salts, pesticides, and trace minerals, including selenium. In 1981, the drainage system became Kesterson`s sole source of water. In 1982, hundreds of dying birds and deformed or stillborn embryos were discovered at Kesterson Reservoir, National Wildlife Refuge, California. Studies revealed high concentrations of selenium in the drainage water entering the reservoir.

Selenium is a trace element that naturally occurs in west side soils. As it bioaccumulates in the food chain, it can reach toxic levels in waterfowl. The problems at Kesterson attracted national attention and alerted the public to agricultural drainage problems throughout the West. Reclamation halted the drainage flow to Kesterson in 1986 and cleaned up and filled in the contaminated ponds.

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During dry and wet cycles, produce of all varieties still thrives in Westlands. Fifty-three varieties of crops were marketed in WWD in 1992. WWD produced $16.5 million worth of almonds, $18.3 million in garlic, and $11.5 million in wine grapes. Add together the value of all the crops grown on 570,552 acres, and total production in 1992 came to $614.8 million.

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Last updated: Apr 21, 2011