The San Luis Unit is part of both the federal Central Valley Project and the California State Water Project. Authorized by the San Luis Act in June 1960 (Public Law 86-488), it is jointly operated by the Bureau of Reclamation and the California Department of Water Resources.
The principal purpose of the San Luis Unit is irrigation water supply for almost 1 million acres of prime farmland in central California. The San Luis Unit is located in California's San Joaquin Valley, which has some of the world’s most productive agricultural lands. Much of the west side of the valley has highly fertile soils that benefit from imported irrigation water; however, clay layers beneath the agricultural lands prevent excess irrigation water from draining deeper into the soil and away from crop roots, negatively impacting agricultural productivity.
Court Rulings In 1995 the U.S. District Court for the Eastern District of California, in litigation brought by landowners in WWD (Sumner Peck Ranch v. Reclamation), concluded that the 1960 San Luis Act imposed a mandatory duty on the Secretary of the Interior to provide drainage service to the San Luis Unit.
In 2000, the U.S. Court of Appeals for the Ninth Circuit upheld the District Court ruling but held that the Department of the Interior has discretion to meet the drainage obligation with a plan other than constructing the drain to the Delta as originally envisioned in the 1954 Feasibility Report for the San Luis Act. In 2001, Reclamation submitted a Plan of Action to the Court outlining a schedule to complete a reevaluation of the drainage service.
Construction of the drain began in 1968 to collect and transport subsurface drainage water from the San Luis Unit to the Sacramento-San Joaquin Bay-Delta. Of the planned 188 miles of drain, only 87 miles were completed. Construction was halted in 1975 because of mounting costs and concerns about the potential water quality effects in the Delta. Agricultural drain water from a 42,000-acre portion of Westlands Water District was conveyed in the San Luis Drain between 1977 and 1985.
Westlands Drainage Settlement
On September 15th 2015, the U.S. Department of Justice and the Westlands Water District signed a settlement agreement that would relieve the United States of significant financial obligations and legal liability regarding agricultural drainage service in Westlands Water District.
Northerly Districts Agreement
A draft agreement between the United States and the Pacheco Water District, Panoche Water District, and San Luis Water District (collectively referred to as the Northerly Districts) would relieve Reclamation of its obligation to provide drainage service to the Northerly Districts. It parallels a September 2015 settlement agreement between the U.S. and Westlands Water District, and in combination with the Westlands settlement, would fully relieve the U.S. of its obligation to provide drainage service within the San Luis Unit of the Central Valley Project, if enacted into law.
The San Luis Unit’s joint-use facilities include:
- O'Neill Dam and Forebay
- B.F. Sisk San Luis Dam
- San Luis Reservoir, and
- San Luis Canal
The federal-only features include:
- O'Neill Pumping Plant and Intake Canal
- Coalinga Canal, and
- San Luis Drain
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