oil reservoir in the field itself. One of the largest of these, a 225-megawatt facility, was built by the Sun Cogeneration Company and a subsidiary of Southern California Edison on the western boundary of the field, along Crocker Springs Road. A construction permit was approved in 1987 and the plant began operation two years later; it is now known as the Midway-Sunset Cogeneration Company. The State Energy Commission only allowed construction of the plant after environmental mitigation measures, including habitat protection for several endangered species living in the vicinity, including the San Joaquin kit fox. In 2008, the company operating the plant refunded $85.7 million to the State of California in a claim lingering from the time of the 2000–2001 California Energy Crisis. Other cogeneration plants on the Midway-Sunset field include the Dome Project by Nuevo Energy (now Plains Exploration & Production); Aera Energy LLC; Midset Cogeneration; the Arco Oxford plant near Fellows; a Chevron plant in the hills south of Taft; the M.H. Whittier plant east of Taft; and the Monarch, Berry Petroleum, and Chalk Cliff Cogeneration plants between Maricopa and Taft. Production history and future potential The Midway-Sunset field continued as California's top producing field in 2012, with produced, down from in 2011. The estimated ultimate size of the Midway-Sunset oilfield resource has been repeatedly raised during its more than 120 years of production. The first published estimate of its size was just under in the 1930s. New reservoirs continued to be discovered into the 1950s. In the early 1960s, operators began pilot cyclic steam injection, which proved successful, and steam flooding in the 1960s and 70s worked even better. Reserves were revised upward repeatedly beginning in the late 1960s (see chart, left). An upward revision in 1991 of of oil was followed in 1999 by another jump in reserves of more than . From 1988 to 1998, about 80 percent of the oil produced at Midway-Sunset ( of produced) was "incremental" production attributable to enhanced recovery. It seems likely that additional reserve additions can be made, if operators are successful in further improving enhanced oil recovery techniques. Estimated conventional oil reserves Through the end of 2009, of oil had been extracted from the field, leaving an estimated of recoverable oil remaining. The remaining oil amounted to 17% of California's total estimated reserve of . Notes References California Oil and Gas Fields, Volumes I, II and III. Vol.