III. GENERAL DESCRIPTION OF ENVIRONMENTAL SETTING Section 15125 of the California Environmental Quality Act (CEQA) Guidelines requires that an EIR include a description of the existing environment. This section is intended to give a general overview of the environmental setting for the Hidden Creeks Estates project. More detailed information on existing conditions is provided under each individual environmental topic studied in Section IV, Environmental Impact Analysis. This section also provides an overview of related projects that are considered as part of the future conditions in evaluating cumulative impacts. A. OVERVIEW OF ENVIRONMENTAL SETTING 1. Project Site and Surrounding Area Location The Hidden Creeks Estates project site is located in the northern part of the San Fernando Valley at the base of the Santa Susana Mountains. The site is bound by the Santa Susana Mountains to the north and east, and the Simi Hills to the west. The site elevation ranges from approximately 1,500 to 2,700 feet above mean sea level as measured from the US Geological Survey 7.5-Minute Oat Mountain Quadrangle Topographic Map (USGS, 1951, revised 1969). Existing Land Uses The project site consists of approximately 285 acres of hilly terrain. The site currently contains two ranches: one for cattle and one for horses, and several experimental dwelling units. The Hidden Creeks Ranch has also been occasionally used as a location for the filming of television and movie productions and contains some sets built for filming on the southern end of the ranch. The Hidden Creeks Ranch, one of two ranches on the property, primarily consists of open space and grazing land for cattle. Approximately 40 head of cattle currently use the ranch for grazing. A filming set is located near the southern end of the ranch. Two small cabins, a barn, and other structures are also present on the ranch. The Mountain Meadow Ranch, the second of the two ranches on the project site, boards approximately 80 horses. This 12-acre ranch consists of a ranch house, stables, corals, a barn, and tack sheds. Located south of the two ranches are several unoccupied experimental residential units. The residences were constructed to test the use of Styrofoam as residential insulation. Impact Sciences, Inc. III-1 Hidden Creeks Estates Draft EIR 860.01 April 2008 III. Environmental Setting County of Los Angeles General Plan Land Use and Zoning Designations Currently the Hidden Creeks Estates project site is located within an unincorporated area of the County of Los Angeles; therefore, land use is governed by the County of Los Angeles Zoning Ordinance and the County of Los Angeles General Plan. According to the County General Plan, the land use designation for the project site is Non-Urban. According to the County of Los Angeles Zoning Ordinance, the zoning designation for the project site is A-2-1. This zoning designation allows for light and heavy agriculture uses, as well as single family residences, crops, greenhouses, the raising of cattle, horses, sheep, goats, poultry, birds, earthworms, the operation of animal hospitals, dairies, dog kennels, livestock feed lots, manure spreading, and oil wells. Surrounding Land Uses The project site is located adjacent to the City of Los Angeles. Immediately east of the project site is City of Los Angeles land that includes a strip of open space as well as land currently being developed with an additional implementation phase of the Porter Ranch Specific Plan. Further to the east is the community of Porter Ranch. Located immediately north of the project site is additional undeveloped County of Los Angeles land. Further north of the project site are the Santa Susana Mountains. Located west of the project site is the Michael D. Antonovich Regional Park at Joughin Ranch, which is dedicated open space, and beyond the Michael Antonovich Park is the Los Angeles-Ventura County line and additional undeveloped open space. South of the project site is Browns Canyon Road, which provides local access to ranches and equestrian centers within Browns Canyon. Further south of the project site is the Ronald Reagan Freeway (SR-118) and the San Fernando Valley. Watershed The project site is located within the Bull Canyon sub-watershed, which is tributary to the Los Angeles River Hydrological Unit, which itself is located within the South Coast Hydrologic Region. The size of the watershed is approximately 2,250 acres, or approximately 3.5 square miles. The project site is located near drainage headwaters, where steep, erosional, generally south-draining faces direct water toward the project site. Topography Elevations within the Hidden Creeks Estates property range from approximately 2,145 feet above mean sea level in the northernmost extent of the property to 1,350 feet in the southernmost, at the confluence of the Browns Canyon Wash and Mormon Canyon. Topography on the site ranges from rolling hills with slopes of 5 percent or less to steep hillsides and highly eroded streambanks with maximum slopes in Impact Sciences, Inc. III-2 Hidden Creeks Estates Draft EIR 860.01 April 2008 III. Environmental Setting excess of 60 percent. Erosional surfaces are the major landscape feature found throughout the property. Steep hillsides, naturally erodable and unconsolidated soils, and the long-term impacts of cattle grazing (such as loss of native vegetation, soil compaction, eroded streambanks, decreased rainwater infiltration, and increased overland surface flows) have all resulted in landscape features associated with high levels of erosion. These features include slumped hillsides, a number of ephemeral washes, and the formation of deeply eroded gullies with concomitant soil and vegetation loss. Hydrology Water is the driving force in creating and sustaining stream habitat and riparian vegetation. Apart from the two primary channels of Mormon Canyon and Browns Canyon Wash, the dominant water sources for the project site are surface and subsurface flows originating within the boundary of the project site. Additional water sources include runoff from the Santa Susana Mountains to the north, most notably within the Mormon Canyon and Browns Canyon Wash channels. In general, directional flows are oriented to the south. The project site is located in two distinct watersheds: Mormon Canyon to the east and Browns Canyon Wash to the west. The eastern half of the project site contains the upper headwaters of three tributaries to Mormon Canyon, as well as three segments of the mainstem of Mormon Canyon. The western half of the project site contains one tributary to Browns Canyon Wash and two segments of the mainstem of Browns Canyon Wash. Additionally, the project site contains the confluence of the two main streams where Mormon Canyon enters Browns Canyon Wash. The upstream reaches of both Mormon Canyon and Browns Canyon Wash are located off the project site to the northeast and northwest respectively. The dominant hydrologic feature on the project site is gently to steeply eroded ephemeral washes tributary to the two primary channels. In general, erosional forces within the tributaries steadily increase moving downstream, and then decrease prior to entering the main channels. Both Browns Canyon Wash and Mormon Canyon flow through steep-walled canyons upstream and north of their convergence at the southernmost edge of the project site. Other hydrologic features on the project site include a limited number of flat and depressed areas that contain vegetative and hydrologic characteristics associated with both seasonal and permanent wetlands. Soils Soils within the property boundary, as mapped by the Natural Resources Conservation Service (NRCS), are Balcom and Gazos series silty clay loam with slopes between 15 and 50 percent. Additionally, a small distribution of Lopez series shaley clay loam with slopes of 30 to 50 percent exist outside the property boundary, but within an area of interest. Impact Sciences, Inc. III-3 Hidden Creeks Estates Draft EIR 860.01 April 2008 III. Environmental Setting Biological Resources Vegetation The combination of topography, hydrology, and land use dictates the extent and type of vegetative communities found on the project site; specifically, vegetative types are largely determined by relative slope, the location of surface and subsurface flows, and the presence/absence of cattle grazing. A total of 14 plant communities have been identified on the project site. These include non-native grassland, mixed sage scrub, coastal sage chaparral scrub, California sagebrush scrub, chamise chaparral, coast live oak woodland, California walnut woodland, mixed California walnut-coast live oak woodland, mixed willow riparian woodland, mixed coast live oak-willow riparian woodland, mulefat scrub, tamarisk scrub, bulrush-cattail wetland, and disturbed areas that have been built upon, mowed, or plowed. Upland Vegetation The vast majority of the project site is comprised of upland vegetative communities. In general, on-site upland vegetation can be divided into two categories: vegetation readily accessed by cattle and thus impacted by grazing; and inaccessible vegetation that exhibits little to no grazing impacts. Areas heavily grazed include easily accessed, gentle- to medium-sloped hillsides, ridges, and plateaus. Non-native grassland dominates these areas. Areas marginally impacted by grazing include dry, steep hillsides in which sparse groundcover and the lack of regular grazing allow native vegetation to persist. In general, somewhat disturbed scrub communities,