The Carrizo Plain is a large enclosed grassland plain, approximately 50 miles long and up to 15 miles across, in southeastern San Luis Obispo County, California, about 100 miles northwest of Los Angeles. It contains the 246,812 acre Carrizo Plain National Monument, and it is the largest single native grassland remaining in California. The San Andreas Fault bisects it it.
The Colony of Calsahara is located entirely within the plain.
Geography and geology
The plain extends northwest from the town of Maricopa, following the San Andreas Fault. Bordering the plain to the northeast is the Temblor Range, on the other side of which is the California Central Valley. Bordering the plain to the southwest is the Caliente Range. The community of California Valley is on the northern part of the plain. The average elevation of the plain is about 2,200 feet (670.6 m). Soda Lake, a 3,000-acre (12 km2) alkaline lake, is in the center of the plain with the popular Painted Rock containing Chumash and Yokut rock art nearby. As the central depression in an enclosed basin, Soda Lake receives all of the runoff from both sides of the plain. At 5,106 feet (1,556 m), Caliente Mountain, southwest of the plain, stands as the highest point in San Luis Obispo County. The climate type of the Carrizo Plain is semi-arid grassland. No trees grow there and the annual rainfall is around 9 inches (230 mm) per year.
The Carrizo Plain is an easily accessible place to see surface fractures of the San Andreas Fault; they are clearly visible along the eastern side of the plain, at the foot of the Temblor Range. They are best seen in early morning and evening light, when shadows enhance the topography. In addition to its spring wildflower displays, Carrizo Plain is famous for Painted Rock, a sandstone alcove adorned with pictographs created by the Chumash people around 2000 BC.
Wallace Creek is a small stream, draining into Soda Lake, that remains dry most of the year. It drains perpendicular to the San Andreas Fault, and the creek bed is currently offset by 425 ft (130 m) due to the movement of the fault. About 23 ft (7 m) of the displacement was created during the 1857 Fort Tejon earthquake. The current segment began forming 3,700 years ago. Sometime between 1540 and 1630 A.D., the creek was offset by about 40.6 feet (12.4 m) feet in an even larger earthquake.
Two other older creek beds lie 1,560 and 1,310 ft (475 and 399 m) northwest along the San Andreas Fault. The first creek bed was created around 13,000 years ago when climate change formed the creek on a large active alluvial fan. The second bed was created about 11,000 years ago.
The creek has been carefully studied by geologists to find a correlation between the offset and historical events, such as earthquakes, that have occurred along the San Andreas Fault. Although Wallace Creek is not the only creek that has been offset by the San Andreas Fault, it is the most spectacular.
The Carrizo Plain is home to 13 species listed as endangered either by the state or federal government, the largest concentration of endangered species in California. Some of these species include the San Joaquin kit fox, the San Joaquin antelope squirrel, the blunt-nosed leopard lizard, the giant kangaroo rat, greater and lesser sandhill cranes, and the California condor. The tule elk, pronghorn, black-tailed jackrabbit, western coyotes, and Le Conte's thrasher all also make their homes in the Carrizo Plain. The hotter climate and ecology of Carrizo Plain allows the Le Conte's thrasher of the Southwestern United States to have a small disjunct range farther north than normal.
- San Joaquin kit fox – a small nocturnal subspecies of the kit fox that was formerly common throughout the San Joaquin Valley but has recently become endangered.
- Blunt-nosed leopard lizard – a small, 3–5 inch gray to brown lizard with large dark spots and cream-colored cross bands. It has a broad, triangular shaped head and is endemic to California. It inhabits the grasslands and alkali flats of the San Joaquin Valley and the surrounding foothills and valleys.
- Giant kangaroo rat – the largest of all kangaroo rats. The giant kangaroo rat is also endemic to California and now only occupies about 2% of its original range, making it critically endangered.
- San Joaquin antelope squirrel – a light tan squirrel with a white belly and a white stripe down its back and sides. Most of its habitat is used for agriculture, making the Carrizo Plain the habitat for most of the remaining population.
The remote Carrizo Plain's status as one of the sunniest places in the state was exploited by the solar power industry from 1983 to 1994. This was by far the largest photovoltaic array in the world, with 100,000 of the 1-by-4-foot (0.3 by 1.2 m) photovoltaic arrays producing 5.2 megawatts at its peak. The plant was originally constructed by the Atlantic Richfield oil company (ARCO) in 1983. During the 1979 energy crisis ARCO became a solar energy pioneer, manufacturing the photovoltaic arrays themselves. ARCO first built a 1 megawatt pilot operation, the Lugo plant in Hesperia, California, which is also now closed. The Carrizo Solar Corporation, based in Albuquerque, New Mexico, bought the two facilities from ARCO in 1990, but the price of oil never rose as was predicted, so the solar plant never became competitive with fossil fuel-based energy production. Carrizo Solar sold its electricity to the local utility for between three and four cents a kilowatt-hour, while a minimum price of eight to ten cents a kilowatt-hour would have been necessary in order for Carrizo to make a profit. Another photovoltaic facility was planned for the site by the Chatsworth Utility Power Group; with an output of 100 megawatts, it would have been many times larger than the existing facility, but the facility never got off the drawing board. The Carrizo Solar Company dismantled its 177-acre (0.7 km2) facility in the late 1990s, and the used solar panels are still being resold throughout the world.
In October 2007, the Palo Alto company Ausra, doing business as Carrizo Energy, filed an application for a 177 MW (peak) Carrizo Energy Solar Farm (CESF) on 640 acres (2.6 km2) adjacent to the previous ARCO site. Instead of photovoltaic cells (as used by ARCO), however, Ausra will use Fresnel reflectors that concentrate solar energy onto pipes in a receiver elevated above the ground. The concentrated solar energy boils water within a row of specially coated stainless steel pipes in an insulated cavity to produce saturated steam. The steam produced in the receivers is collected in a series of pipes, routed to steam drums, and then to the two turbine generators. Steam used by the steam turbines is condensed into liquid water and then returned to the solar field. Electricity from the steam generators will be used in San Luis Obispo county. Local opposition to some solar farm proposals centers on concerns about height above grade, noise and heat plume.
The solar field would have operated daily from sunrise to sunset. Typical operating hours for the CESF would have been approximately 13 hours per day, or an average of 4,765 hours per year. In November 2009, the project was canceled.
On August 14, 2008, Pacific Gas and Electric Company announced agreements to buy the power from two proposed photovoltaic plants in the Carrizo Plain, Topaz Solar Farm and High Plains Ranch, with a combined peak power of 800 MW. If built, these will be the largest photovoltaic plants in the world.
As of November 2014 Topaz Solar Farm is operational, with peak power of 550 MW.