often the capping impermeable formation, underneath which oil collects, but in some areas it is a productive unit in its own right. Its average depth is . One of the next reservoirs to be discovered was the Gusher Pool, which, when found in 1909, took its name from the event itself: a large oil gusher. This occurrence was eclipsed spectacularly the next year, when drillers found the Lakeview Pool, unexpectedly drilling into a reservoir of oil under intense pressure, later estimated at approximately from the heights attained by the spewing oil. The resulting Lakeview Gusher was the longest-lasting and most productive oil gusher in U.S. history. Drillers continued to find new oil reservoirs throughout the 20th century, with new discoveries still occurring in the 1980s. Most reservoirs occur in the Miocene-age Monterey Formation, with depths usually to , although one discovery, the "PULV" Pool of 1979, was below ground surface. The only well developed at this depth, and the only well in the PULV pool, was abandoned a year after it was drilled. Operations The principal operators of Midway-Sunset, as of 2008, were Aera Energy LLC and the Chevron Corporation. Other operators on the field included large firms such as Occidental Petroleum and Plains Exploration & Production, as well as numerous independents, such as Breitburn Energy, Berry Petroleum, E&B Natural Resources, Crimson Resource Management. As of the end of 2008, the most recent date for which data was available, the field contained 11,494 producing wells, more than any other oil field in California (the Kern River Field was second at 9,689). A traveler along State Route 33 between Maricopa and McKittrick will see hundreds of pumpjacks, the relatively small proportion of the oil wells that are visible from the highway. Several enhanced oil recovery technologies have been employed at Midway-Sunset. Since the oil is heavy, and does not flow freely, it can be assisted by thermal methods, which include steamflooding, cyclic steam, and fire flooding. Waterflooding is also used to boost reservoir pressures. Cogeneration As the Midway-Sunset field has a large amount of heavy oil requiring steam to allow its recovery, many of the field operators have built cogeneration plants to both sell power to the electric grid and create steam for their operations. This kind of power plant burns natural gas, abundantly available on site, and converts the energy into both electricity and steam used to flood the heavy