4.5 Eldorado Valley
The Eldorado Valley is southwest of Boulder City, Nevada. U.S. Highway 95 to Searchlight, Nevada, transects the valley in a north-south direction. The U.S. Bureau of Land Management patented 107,412 acres of Eldorado Valley to the state of Nevada, at which time this land was transferred to the city of Boulder City. Boulder City has designated 6,000 acres of this land for a Solar Enterprise Zone facility (DOE/NV, 1994b). This zone is excluded from a conservation easement within these transferred lands that is managed for the conservation, protection, restoration, and enhancement of the desert tortoise and its habitat. The DOE would enter into a partnership agreement with the solar industry, Nevada stakeholders, and university systems to develop the solar-generating facilities.
4.5.1 Land Use
Land in Eldorado Valley is used for a limited number of activities as discussed in the following Land-Use Designations section. Also discussed in this section are the site-support activities related to Eldorado Valley.
4.5.1.1 Public Land Orders and Withdrawals.
This section is not applicable to Eldorado Valley.
4.5.1.2 Land-Use Designations.
Land use in Eldorado Valley is limited primarily to grazing,light industry, and recreational use, including a raceway and windsurfing. Active grazing permits have been issued by the U.S. Bureau of Land Management for the Ireteba Peaks, McCullough Mountains, and Hidden Valley allotments. The Iretaba Peaks and McCullough Mountains allotments have historically provided forage for almost 2,300 animal unit months. The McCullough Mountains allotment is operated by the Nature Conservancy. There is some limited light industry in the northwestern-most part of the basin. The playa area is used for recreation, especially land sailing, and a raceway is situated near the southern end of the playa.
4.5.1.3 Site- Support Activities.
Site support in the Eldorado Valley includes three power substations and transmission lines and two natural gas pipe lines. FACILITIESNo facilities currently exist at the proposed location of a Solar Enterprise Zone facility in Eldorado Valley. UTILITIESTwo existing 500-kV substations and a third substation under construction are within a few miles of the proposed Solar Enterprise Zone facility in Eldorado Valley: Southern California Edison's Eldorado Substation, Los Angeles Department of Water and Power's McCullough Substation, and the Marketplace Switching Station. When the Marketplace Switching Station is completed, these substations will connect the transmission systems of California, southern Nevada, and Arizona (DOE/NV, 1994b). Two major Southwest Gas natural gas pipe lines transect Eldorado Valley. One pipe line is immediately adjacent to U.S. Highway 95, and the other pipe line is approximately 2 km (1 mi) west of the highway. Depending on where the proposed Solar Enterprise Zone facility is sited, the pipe lines could be immediately adjacent or up to 10 km (6 mi) away. Both pipe lines are main supply lines for the Las Vegas area and consequently are insufficient to support the Solar Enterprise Zone facility during winter months. An additional 51-cm (20 in) pipe line from an existing main line would be necessary; the nearest main gas pipe line is anEl Paso Gas pipe line south of Laughlin, Nevada, 110 km (68 mi) away (DOE/NV, 1994b). SERVICESServices discussed for Eldorado Valley include law enforcement and security, fire protection, and health care. Law Enforcement and SecurityEldorado Valley is not secured or restricted. Law enforcement is provided by the Clark County Sheriff's Department. Fire ProtectionFire protection for Eldorado Valley is provided by the U.S. Bureau of Land Management. Health CareFor health care, first aid stations would be located near field activities, if required.
4.5.1.4 Airspace.
Eldorado Valley is located underneath the southeastern portion of the Las Vegas Class B airspace that begins at 2,438 m (8,000 ft) mean sea level. All aircraft operating in this area must be under positive control of Las Vegas Approach Control (see Section 4.1.1.4 ).
4.5.2 Transportation
This section presents existing transportation at Eldorado Valley. Transportation is discussed with respect to on-site traffic, off-site traffic, transportation of materials and waste, and other transportation.
4.5.2.1 On-Site Traffic.
This section is not applicable for Eldorado Valley.
4.5.2.2 Off-Site Traffic.
U.S. Highway 95 runs north-south through Eldorado Valley and is a single lane in each direction. At the northern end of the valley, U.S. Highway 95 intersects U.S. Highway 93 approximately half the distance between Boulder City, Nevada and Henderson, Nevada. U.S. Highway 93/95 continues northwestward through Henderson and through Las Vegas where it intersects Interstate 15. At the southern end of the valley at Searchlight, Nevada, U.S. Route 95 intersects east-west trending State Route 164, also a single lane in both directions. State Route 164 intersects Interstate 15, 52 km (32 mi) west of Searchlight. U.S. Route95 continues south of Searchlight for 30.6 km (19 mi), where it intersects State Route 163, and continues an additional 39 km (24 mi) south where it intersects U.S. Highway 40 at Needles, California. From U.S. Highway 95, State Highway 163 continues 34 km (21 mi) to Laughlin, Nevada, where it continues east through Arizona to Kingman as State Route 68. In 1993, U.S. Route 95 just south of Boulder City had an average annual daily traffic of 6,600 vehicles and operated at a level of service B.
4.5.2.3 Transportation of Materials and Waste.
Transportation of waste and materials at a Solar Enterprise Zone facility location is not expected. Therefore, this section is not applicable.
4.5.2.4 Other Transportation.
Air or rail transportation of workers or materials to Eldorado Valley has not been proposed; therefore, these facilities have not been examined in detail. The nearest rail line to the Eldorado Valley site is the Union Pacific line in Boulder City, which connects Boulder City with Las Vegas. No rail spur exists on a Solar Enterprise Zone facility site. Airfield facilities do not exist on the site. The nearest airfield is in Boulder City. Traffic information in the vicinity of a Solar Enterprise Zone facility in Eldorado Valley is presented in Section 4.5.2.2 , Off-Site Traffic.
4.5.3 Socioeconomics
Eldorado Valley is located within Clark County, and this county's existing socioeconomic conditions are addressed and characterized in Section 4.1.3 .
4.5.4 Geology and Soils
Physiography, geology, and soils are addressed in this section. Also briefly discussed are seismic activities and geologic resources.
4.5.4.1 Physiography. Eldorado Valley is a topographically closed basin of 1,373 km² (530 mi2)
(see Figure 4-59 ). Elevations range from about 2,152 m (7,060 ft) on the west at McCullough Mountain to 521 m (1,708 ft) at the playa in the north-central part of the valley. On the east, the Eldorado Mountains rise to elevations only slightly above 1,524 m (5,000 ft). On the south, Eldorado Valley is separated from Paiute Valley by the Highland Range and unnamed highlands of the Searchlight district. On the north, Eldorado Valley is bounded by the Black Hills and the River Mountains. On the valley floor, the dominant feature is the playa in the north-central part of the basin and the numerous washes that drain the upland areas. Figure 4-59. Eldorado Valley and surrounding area
4.5.4.2 Geology.
The general geologic conditions and mineral deposits of Eldorado Valley have been detailed by the Nevada Bureau of Mines and Geology (Longwell, et al., 1965). The general geology of Eldorado Valley includes a number of geologic units. The rocks and valley-fill deposits may be categorized into five types: (1) alluvial deposits, (2) older gravels, (3) volcanics, (4) granite, and (5) metamorphics. Alluvial deposits occur in the valley-floor area and include interbedded sequences of gravel, sand, silt, and clay. These deposits are generally unconsolidated, but may be cemented in the vicinity of fault zones or where mineralized water is present. A test well near the playa penetrated more than 305 m (1,000 ft) of alluvium. Older gravels of Late Tertiary to Early Quaternary age crop out near the Searchlight area. These deposits are generally weakly consolidated, but include well-lithified fanglomerates, conglomerates, and arkoses. Volcanic rocks of Quaternary, Tertiary, and Cretaceous ages crop out in the mountain masses of the northern half of the McCullough Range, the entire Highland Range, and in the northeastern Eldorado Mountains. Where present, the volcanic rocks reach thicknesses of 610 m (2,000 ft) to 1,219 m (4,000 ft) in some areas. These rocks include a number of discrete geologic units, including andesite, rhyolite, diorite, and tuff. Granitic rocks of Tertiary and Precambrian age (including granites, quartz monzonites, and porphyritic granites) occur in the central and southern Eldorado Mountains. Granitic rocks of Tertiary and Precambrian age probably also form the basement complex under most of the valley. The thickness of granite is not known, but probably exceeds 1,524 m (5,000 ft). Metamorphic rockscomprising schists and gneisses of Precambrian age and metavolcanics of possible Precambrian age occur throughout the southern half of the McCullough Range. The thickness of these rocks is generally less than 610 m (2,000 ft). The major geologic structures in Eldorado Valley include normal faults in the McCullough Range and Eldorado Mountains and in the Highland Springs Anticline in the northwest Highland Range. The major recognized faults include the McClanahan Fault in the McCullough Range and the Jeep Pass, Hidden Valley, Eldorado, and Welcome faults in the Eldorado Range. GEOLOGIC RESOURCESPotential mineral resources in Eldorado Valley include fluid minerals (oil, gas, and geothermal resources), nonenergy leasable minerals (primarily sodium and potassium compounds), salable minerals (common sand, gravel, and rock), and locatable minerals (metallic and nonmetallic mineral deposits). The U.S. Bureau of Land Management (BLM, 1992) has defined the level of potential for development of these mineral types. The potential for geothermal is low and, although the oil and gas potential has been categorized by the U.S. Bureau of Land Management as moderate, there is only one oil lease within the valley. This area is located in the Railroad Pass area in the northernmost part of the basin. No oil or gas exploratory wells have been drilled in the basin. The U.S. Bureau of Land Management (BLM, 1992) has categorized the sodium and potassium potential of Eldorado Valley as moderate in the north-central part of the basin and low elsewhere. Much of the area in the vicinity of the Eldorado playa has a high potential for salable minerals, primarily sand and gravel, with the rest of the areas of alluvium classified as having moderate potential. In the consolidated rock areas of the Eldorado Mountains and McCullough Range, the potential for salable minerals is low. The potential for locatable mineral resources is low over much of the valley. The potential for locatable resources is moderate in the McCullough Range and northern Highland Range, and high in the Eldorado Mountains and southern Highland Range. Eldorado Valley contains portions of three mining districts: the Searchlight District, the Eldorado Canyon District, and the Alunite (Railroad Pass) District. Although production has been limited since the early 1950s, interest in these areas continues. The Searchlight District has been the most active, having produced millions of dollars worth of gold, silver, copper, and lead since 1897. Mining in the Eldorado District, located in and around Nelson, was initiated in 1857, and has since produced millions of dollars worth of gold, silver, copper, lead, and zinc. The Alunite District is located about five miles east of Boulder City and historically has produced minor amounts of gold, silver, and lead. Alunite is also present in the district, but has not been successfully developed. Because of the presence of these mining districts, hundreds of mining claims have been filed within Eldorado Valley. The Nevada Department of Transportation maintains about 10 material site rights-of-way in the valley, and there is 1 community pit.
4.5.4.3 Soils.
The soils in Eldorado Valley are very deep, medium-textured saline and alkaline soils in the lowland areas; shallow, gravelly coarse-textured soils over the alluvial fans; and discontinuous, rocky gravelly coarse-textured soils in the mountain areas (BLM, 1992). The soils in Eldorado Valley are susceptible to erosion by wind and water. The potential for erosion is generally slight except where the soils have been disturbed or along the banks of washes. There is also the potential for localized landslides on the steep slopes of the upland areas. The erosion susceptibility of the soils in Eldorado Valley ranges from low to moderate (BLM, 1992). Most of the erosion condition ranges from slight to moderate, but two areas of critical erosion condition have been identified within the basin.
4.5.5 Hydrology
Discussion of hydrology is divided into surface water and groundwater. Water supply in the vicinity is also discussed.
4.5.5.1 Surface Hydrology.
The surface water resources of Eldorado Valley are very limited. Although not known, the annual runoff within the basin has been estimated at less than 1.0 x 105 m3/yr (100 acre-feet/year) (Scott et al., 1971). Surface water runoff is very infrequent, occurring as ephemeral flow in the streambeds and, even less often, as ponded water on the playa in the north-central part of the basin. Surface water runs from the Boulder City Sewage Treatment Plant to the playa area. Flooding characteristics are probably similar to those in adjacent basins; i.e., shallow flash flooding over large areas.
4.5.5.2 Groundwater.
Eldorado Valley is situated within the Las Vegas Flow System, a subsystem of the regional Colorado Flow System (Harrill et al., 1988). Groundwater that originates as precipitation over areas of higher elevation generally flows toward the axis of the basin and then north into Las Vegas Valley or eastward into the Colorado River Valley. (Harrill et al; 1988) indicate that an estimated 1.2 million m3/yr (1,000 acre-feet/year) discharge into the Colorado River Valley. Groundwater under Eldorado Valley occurs at depths ranging from about 84 to 98 m (275 to 320 ft) below land surface in the north-central part of the basin (Buqo and Giampaoli, 1988). The depth to water may be greater under the higher portions of the alluvial aprons that bound the valley floor. The groundwater is derived from two sources: recharge over the basin is 1.0 x 106 m3/yr (1,100 acre-feet/year) and subsurface inflow from Hidden Valley (Rush and Huxel, 1966). The recharge derived from flow from Hidden Valley is believed to be minor; i.e., less than 370,050 m³/yr (300 acre-feet/year) (Rush and Huxel, 1966). Although there are a number of springs in the upland areas of Eldorado Valley, the combined discharge rate of these springs is small. The more significant springs include McCullough and Ora Hanna Springs in the McCullough Range; Cow Spring in the Highland Range; and Tule, Bridge, and Forlorn Horse Springs in the Eldorado Mountains. These springs provide an important source of water and habitat for wildlife. Eldorado Valley is a designated groundwater basin. The committed groundwater resources of 3.0 x 106 m3/yr (2,390 acre-feet/year) are more than 4 times theperennial yield of 6.0 x 105 m 3/yr (500 acre-feet/year). Mining is by far the largest water user in the basin with total water rights of 3.0 x 106 m 3 (2,400 acre-feet). Small quantities of water (a total of only 3.0 x 104 m 3 or 24 acre-feet) have been appropriated for municipal, quasimunicipal, stock watering, and industrial use (Buqo, 1996). As of October 1994, there were two additional water right applications for 7.0 x 105 m3/yr (540 acre-feet/year). Water supplies in Eldorado Valley can be augmented through the importation of water from Boulder City. According to information presented by the Nevada Solar Enterprise Zone task force work group, Boulder City has the capability to provide 1.0 x 106 m 3/yr (1,000 acre-feet/year) to 3.0 x 106 m 3/yr (3,000 acre-feet/year) of treated effluent or irrigation water to meet water demands in Eldorado Valley. WATER QUALITYGroundwater in Eldorado Valley is predominantly a sodium-bicarbonate type with high concentrations of total dissolved solids and a medium to high salinity hazard (Rush and Huxel, 1966). Historic analyses of the groundwater from wells in Eldorado Valley indicate that concentrations of total dissolved solids, sulfate, and chloride exceed drinking water standards in some areas. Although data are generally lacking for metals and other trace constituents for the area, the presence of historic mining districts suggests that these constituents may be present in the groundwater in the vicinity of former mining areas. Iron, lead, manganese, mercury, and nitrate have been detected in groundwater at levels exceeding their respective maximum contaminant levels in the Searchlight area, according to information on file with the Clark County Department of Health Services (Buqo and Giampaoli, 1988).
4.5.6 Biological Resources
The scientific names of plants and animals mentioned in this section are given in Chapter 2 of Appendix E , Biological Resources. The Eldorado Valley is within the Mojave Desert. Creosote bush and white bursage are the dominant shrub species within the Solar Enterprise Zone. Dry washes in this area often have stands of catclaw acacia. To the north of this area, on the fine-textured saline oralkaline soils close to the playa, four-wing saltbush, shadscale, green ephedra, seep weed, and bud sage are the dominant plants (BLM, 1992). Common animal species are similar to those described for the Mojave Desert habitats on the NTS. This site is not habitat for mule deer or bighorn sheep (BLM, 1992), although these species do occur in some of the surrounding mountain ranges. The threatened desert tortoise is the only threatened or endangered species that occurs at this site (U.S. Fish and Wildlife Service, 1994). The density of desert tortoises in the area was estimated at 8 per km2 (20 per mi2). This site occurs immediately adjacent to the Paiute-Eldorado Critical Habitat Unit for the desert tortoise (U.S. Fish and Wildlife Service, 1994). The site is not a critical habitat for the desert tortoise (U.S. Fish and Wildlife Service, 1994). The Paiute-Eldorado Critical Habitat Unit lies immediately east and south of the site. The site was excluded by Boulder City from a conservation easement granted to Clark County for the conservation, protection, restoration, and enhancement of the desert tortoise. This easement (85,617 acres) surrounds lands designated for a Solar Enterprise Zone facility. No current candidate plant or animal species (61 FR 7596) are known to occur within the Eldorado Valley site. The banded gila monster, a state-protected species, may occur in this area (BLM, 1992). No plant species are known to occur within the Eldorado Valley site that have been listed as threatened, endangered, or candidate under the Endangered Species Act or by the state of Nevada (16 U.S.C. 1531, 1973; BLM, 1992; 58 FR 188, 1993; NAC, 1994).
4.5.7 Air Quality and Climate
This section includes a description of the air quality conditions at Eldorado Valley, including climatology, meteorology, and ambient air quality. CLIMATOLOGY AND METEOROLOGYAlthough there are no weather stations in Eldorado Valley, the climate can be represented on the basis of stations in Boulder City and Searchlight. In general,Eldorado Valley exhibits the low humidity and low annual precipitation characteristic of the climate of Clark County. The warmest month is July, when the mean monthly maximum temperature is 40 °C (104 °F), and January is the coolest month with a mean monthly minimum of 0.5 °C (33 °F). The average monthly wind speed ranges from 11 kph (7 mph) in December to 18 kph (11 mph) in April and June. Diurnal variation in wind is common, reflecting the differential heating of the ground. AMBIENT AIR QUALITYEldorado Valley is located within Nevada Intrastate Air Quality Control Region 147, which is designated unclassifiable/ attainment for all criteria pollutants. The closest Class I Prevention of Significant Deterioration area is Grand Canyon National Park, approximately 90 km (56 mi) east of Eldorado Valley. Because Eldorado Valley is largely undeveloped, there are few emission sources in the area. Typical sources include mining and milling operations; off-road vehicle, railroad, and aircraft traffic; and fugitive dust. The closest nonattainment area to the Eldorado Valley is the Las Vegas Valley, which is a nonattainment area for PM10 particulates and carbon dioxide and borderline nonattainment for ozone. Eldorado Valley borders the Las Vegas Valley Air Quality Nonattainment Area on the west and north.
4.5.8 Noise
The acoustic environment of Eldorado Valley can be classified as uninhabited desert or small rural communities (Section 4.1.8 ). Noise measurements have not been made at the Eldorado Valley Solar Enterprise Zone facility site. The major sources of noise would be associated with prevailing meteorological conditions, such as wind. Traffic on U.S. Highway 95, which transects Eldorado Valley just east of the site, also generates noise.
4.5.9 Visual Resources
The landscape character of Eldorado Valley is typical of the Great Basin. Regional topography consists of mountain ranges arranged in a north-south orientation, separated by broad valleys. The existing viewscape includes two Bureau of LandManagement Wilderness Study Areas located in the McCullough Range and one in the Eldorado Mountains, U.S. Highway 95, portions of Boulder City, power transmission lines, gravel quarries, and electrical substations. The Bureau of Land Management Wilderness Study Areas are 8 km (5 mi) from the proposed site. The landscape at Eldorado Valley is common to the region, and because of the amount of cultural modifications, the scenic quality has been designated as Class C. U.S. Highway 95 has an average daily traffic of 5,000 to 7,000 vehicles (NDOT, 1993a). Therefore, Eldorado Valley would have a high sensitivity level.
4.5.10 Cultural Resources
Eldorado Valley lies in southern Nevada, an area with a prehistory that may span the past 10,000 years or more. Properties ranging from the early prehistoric period to historic mining and ranching sites are known. Groups of Southern Paiute and Mohave people lived within or used parts of the project area at the time of first European contact. The Colorado River defines the southern boundary of Southern Paiute territory where it formed the core of Mojave territory (Stoffle and Dobyns, 1982). Southern Paiute groups foraged widely for wild plant foods throughout southern Nevada and also practiced horticulture at select oases in the Las Vegas Valley and on the Virgin and Colorado Rivers. The Chemehuevi, a closely related group, took over much of Mohave Indian traits, including floodplain agriculture, and routinely cooperated with the Mohave in raids against enemies, such as the Cocopa and Halchidhoma. However, the Chemehuevi were occasionally at war with the Mohave themselves (Kelly and Fowler, 1986). The Mohave focused on floodplain agriculture, but also utilized wild plant and animal foods and fish. Geographically, Eldorado Valley extends from Boulder City to Searchlight. The region of influence includes areas south of Boulder City adjacent to U.S. Highway 95 near the junction with State Route 60. A 2,000-acre zone is proposed for a parabolic trough generating station, while existing natural gas pipe line corridors would be used tobring an additional gas supply to the generating station. RECORDED CULTURAL RESOURCESMost of the cultural resources that have been recorded in the previously defined area have resulted from Transmission Line and Powerline Surveys (Dames and Moore, 1985; Rafferty, 1991). Prehistoric sites have been recorded around the perimeter of Eldorado Dry Lake. Two temporary camps have been recorded. One of the sites first recorded by (M.J. Rogers, 1939) includes numerous lithic artifacts and groundstone. Testing conducted in 1990 indicated that only surface deposits occur and that the integrity of the site had been compromised owing to hydraulic action (Dames and Moore, 1985). Both sites were recommended as ineligible for the National Register of Historic Places. Other sites date to the historic period. Most are isolated occurrences of cans, which may have been left behind by prospectors or the Hoover Dam construction workers passing through the area. SITES OF AMERICAN INDIAN SIGNIFICANCEThe CGTO knows that the Eldorado Valley study area contains a wide variety of cultural resources, including plants, animals, and archaeology sites. This knowledge derives from previous American Indian cultural resource studies of the area conducted during the Harry Allen-Warner Valley (Bean and Vane, 1979) and Intermountain Power Project (Stoffle and Dobyns, 1982; Stoffle et al., 1983) studies of American Indian concerns along various proposed power line routes, and the Ivanpah Generating Station study (Bean and Vane, 1982) conducted in a neighboring valley. Identified Indian plants include creosote (Larrea tridentata), desert trumpet (Erigonum inflatum), and Indian tea (Nevada ephedra). American Indian animals include bighorn sheep (Ovis canadensis), desert tortoise (Gopherus agassizii), and speckled rattlesnake (Croatalus mitchellii). The valley is associated with Indian funeral songs associated with the Cry Ceremonial. There are both spiritual and physical Indian trails associated with this valley. Eldorado Valley trails were used by Pahrump and Las Vegas Paiutes to travel to places along the Colorado River, especially Cottonwood Island. Traditional Indian trails are a significant American Indian cultural resource because theywere both physical and spiritual paths (Laird, 1976). The Ivanpah Generating Study concluded that the McCullough Mountains (which define the western edge of Eldorado Valley) are of much concern to American Indian people, both Southern Paiute and Mohave. According to the Ivanpah study, these American Indian people have trails, sacred sites, plants, and animals of cultural importance in the McCullough Mountains, the associated Eldorado Valley, and in the Eldorado Mountains (Bean and Vane, 1982). A 1975 study of the Navajo-McCullough transmission line right-of-way further indicates the presence of traditional-use plants, early Pinto Series-style projectile points, numerous lithic scatters, and grinding stone fragments that "are related to the seed gathering activities possibly of the later Paiute peoples" (Brooks et al., 1975). Previous studies have been geographically limited to a few places within Eldorado Valley or in neighboring areas, so a complete cultural assessment of the Eldorado Valley is not possible without visiting other portions of the valley with American Indian people.
4.5.11 Occupational and Public Health and Safety
The Eldorado Valley site proposed for siting a Solar Enterprise Zone facility is currently undeveloped desert. Baseline health and safety considerations associated with the environment include the potential for heat stroke and exhaustion (primarily during summer months), dehydration, and poisonous spider and snake bites. Other physical hazards include tripping or stumbling hazards associated with the desert terrain.
4.5.12 Environmental Justice
Existing demographic conditions for Environmental Justice are discussed in Section 4.1.12 . This discussion includes conditions for Eldorado Valley.
|
NEWSLETTER
|
| Join the GlobalSecurity.org mailing list |
|
|
|
