Pantex Plant is located in the Texas panhandle, in Carson County, approximately 17 mi northeast of Amarillo (see Figure 1.1-1). Pantex Plant is bounded on the north by Texas Farm-to-Market (FM) Road 293, on the east by FM 2373, and on the west by FM 683. The southern Pantex Plant boundary is located north of U.S. Highway 60.
Pantex Plant occupies about 15,940 acres. About 9,000 acres is developed land used for office buildings, warehouses, laboratories, and test and production facilities. DOE leases about 5,860 acres of land between Pantex Plant and U.S. Highway 60 from the Texas Tech (M&H, 1994). This area serves as a buffer zone for site safety and security. About 1,080 acres of land northeast of the Plant, across FM 293, is reserved for future DOE use. This area contains the ephemeral lake or playa called "Pantex Lake."
Pantex Plant is located in the upper Red River Basin on the southern high plains of the Texas panhandle. The climate in the southern high plains area is characterized as continental steppe in the western portion to subtropical subhumid in the eastern portion (Larkin and Bomar, 1983). Annual precipitation ranges approximately 17 to 22 in/yr, increasing from west to east across the southern high plains. The climate at Pantex Plant is typical of the southern high plains area. The average annual rainfall during the 30-yr period from 1963 through 1992 was 20.34 in. (NOAA, 1993). The National Oceanic and Atmospheric Administration (NOAA) climatic station is located approximately 7 mi east of downtown Amarillo between Amarillo and Pantex Plant. The average snowfall for the period of record was 15.5 in. The mean annual temperature during this period was 57°F, and the average wind speed was 13.5 mph. Prevailing winds are from the southwest at Pantex Plant. Clear to partly cloudy skies occurred on average 71% of the time during this 30-yr period.
The Amarillo area is subject to rapid and large temperature changes, especially during the winter when cold fronts enter the area from the northern Rocky Mountains and great plains (NOAA, 1993). Temperature drops of 50 to 60°F within a 12-hr period are common. Temperature drops of 40°F have occurred within a few minutes.
The humidity typically is low, resulting in high evaporation rates. Evaporation rates for the southern high plains have been reported to range from approximately 72 to 77 in/yr (Larkin and Bomar, 1983). High evaporation causes a higher ground-level humidity than is expected for this region (BMI, 1994). Wind erosion of topsoil is a common occurrence in the Texas panhandle due to moderate winds, light precipitation, and loose soils (BMI, 1994).
Three-fourths of the total annual precipitation falls from April through September, occurring from thunderstorm activity. The average monthly precipitation during the period of record is shown below:
| Month | Precipitation, in. |
|
|
January February March April May June July August September October November December |
0.55 0.67 0.87 1.37 2.89 3.14 2.66 2.99 2.10 1.60 0.82 0.69
|
|
| Total | 20.34 | |
On average, precipitation is received 69 days of the year in the Amarillo area, of which 5 days receive snowfall. Snow usually melts within a few days after it falls. Heavy snowfalls of 10 in. or more occur infrequently, approximately once every 5 yr, and stay on the ground only a few days.
Pantex Plant is located on the very flat, treeless Llano Estacado ("Staked Plain") portion of the southern high plains at an elevation about 3,500 ft above sea level. The mostly sandy plains around Pantex Plant initially were formed by Tertiary gravel deposits that had been carried eastward from the Rocky Mountains. The area is a rolling grassy plain dotted by frequent natural depressions. The immediate ground surfaces around Pantex Plant are essentially level and flat except for natural depressions in which ephemeral playa lakes occur. About 2 to 4 mi north of the Plant, the relatively flat plains become rolling breaks that form the escarpment above the Canadian River. The vegetation is characterized as mixed prairie of native and introduced grasses. The broken and rolling land around Pantex Plant is classified as mixed prairie (Allred, 1956).
The major surface water stream in the vicinity of Pantex Plant is the Canadian River, located about 17 mi north of the facility, which flows in a generally eastward direction into Lake Meredith, a constructed reservoir. There are no known surface water connections that could transport water from Pantex Plant into either the Canadian River or Lake Meredith. Other minor surface water bodies in the area include: (1) Sweetwater Creek, about 50 mi east of the Plant, which drains the eastern edge of the southern high plains; (2) the Salt Fork of the Red River, about 20 mi southeast of the Plant, which also drains the southern high plains; and (3) the Prairie Dog Fork of the Red River, 35 mi southwest of the Plant.
Due to the flat, level topography of the area, streams are not well developed on the Pantex Plant landscape. Throughout the majority of the high plains, runoff from precipitation does not enter local streams. Instead, the water drains into playa basins. The playas generally are as much as 4,000 ft in diameter and can be more than 30 ft deep. These playas typically are emphemeral due to the shallow water (usually <2 ft) and high evaporation rates. Playas are thought to be formed by wind erosion, dissolution of underlying soil carbonate layers, subsidence induced by salt dissolution, and/or soil piping.
Surface water runoff can pick up and redistribute solutes from the ground surface within the watershed. The areal extent of drainage basins in relation to the locations of playas, the Pantex Plant boundary, and some major Plant zones is shown in Figure 2.2-1.
Stormwater runoff occurs to all playas at the Pantex Plant site. Stormwater from Pantex Plant areas enters the playa basins through ditches and as overland flow. Flow into playas on the site may come from industrial or nonindustrial areas (i.e., cropland or pastureland). Playa 1, Playa 2, and Playa 4 receive stormwater runoff from Zones 11 and 12. Playa 3 receives stormwater runoff from the burning grounds.
In addition to the stormwater runoff, Playa 1 receives effluent from the wastewater treatment facility, and Playas 1, 2, and 4 receive industrial wastewaters. Currently there are no industrial discharges to Pantex Lake, Playa 3, or Playa 5; however, past activities have resulted in discharges to these playas. Playa 1 is he only playa onsite that maintains surface water year round.
Pantex Lake, located about 2.5 mi northeast of the main portion of the Pantex Plant site, is controlled by the DOE. Pantex Lake received discharges from the Old Sewage Treatment Plant (OSTP) from 1942 to 1970 via an underground pipeline. The OSTP is no longer in service. Discharge from the existing wastewater treatment facility is directed into Playa 1.
Playa 3 does not currently receive process wastewater discharges, but water and potential contaminants may have been released to Playa 3 due to a overflow from a solvent evaporation pit located at the burning grounds. The solvent evaporation pit was used for disposal of waste oils and solvents contaminated with explosives from 1955 to 1980.
Playa 5 is located on Texas Tech property to the southwest corner of Pantex Plant. Surface water from Pantex Plant does not drain into Playa 5. However, until about 1992, sanitary and industrial wastes from Amarillo Air Base were routed to Playa 5 to provide Texas Tech with a source of irrigation water.
Some stormwater runoff from undeveloped areas on the periphery of Pantex Plant drains into offsite playas. Drainage beyond Pantex Plant boundaries occurs in Basin 1, where runoff from the two north firing sites drains into a playa north of FM 293. Basin 7 drains offsite to the south into Seven Mile Basin. Drainage from Zones 11 and 12 has been rerouted to other basins so the Basin 7 area now consists of only agricultural land. Zone 4, located in Basin 4, drains into Playa 1. Small portions of Basins 5, 6, and 9, as well as an unlabeled basin located west of Basin 2, also drain offsite.
Under normal conditions, the soils in the upland regions of the Llano Estacado do not transmit significant amounts of water to the main water table. The permeability of both the upland soil and the playa basin deposits is low, varying from <0.06 to up to 0.2 in/hr. Most playas are floored with a lens-shaped accumulation of clay. The clay floor may be as much as 30 ft thick near the center, but is much thinner toward the edges of the playa. The soils that develop on these clay floors, when dry, can contain desiccation cracks of up to 6 ft deep.
Occasionally conditions develop that may allow surface water transport to the perched or main Ogallala aquifers. The soils in the playas can contain up to 65% Randall clays and do not readily transmit water. However, when a large amount of water is discharged to the playa, the water surface may extend beyond the Randall clay lines into the surrounding upland soils. The high pressure causes water to move into the soils around the playa. The soils surrounding the playas are either highly calcareous soils or soils derived from local alluvium and are more permeable than the playa soils. Thus, water may infiltrate down to the water table through the annular region around the playas when the water level is high.
Recent studies at Pantex Plant and the surrounding area suggest that the perched and Ogallala aquifers are being recharged by surface water. The primary mechanism for the recharge is runoff transported through surface ditches and stored in the playas (M&H, 1993). Infiltrating surface water probably passes slowly through the clays at the playa floor and more rapidly through the more-permeable soils in the ditches and around the playa floors.
2.2.5.1 Stratigraphy
The Pantex Plant is situated on the southern high plains of the Texas panhandle. Figure 2.2-2 is a generalized stratigraphic column and schematic geologic cross section for the panhandle region. The primary surface deposits at the Pantex Plant are the Pullman and Randall soil series, which grade downward into the Quaternary Blackwater Draw Formation. The Blackwater Draw Formation consists primarily of eolian silt, fine sand, and clay. Well-developed buried soils have been identified throughout the formation with characteristic pedogenic features including carbonate nodules, calcic horizons, and root tubules (Gustavson, 1994). The thickness of the Blackwater Draw Formation at the Pantex Plant is variable, ranging from approximately 50 to 80 ft within the Pantex Plant area.
Underlying the Blackwater Draw Formation is the Ogallala Formation, which consists of alluvial sands, silt, clay, gravel, and several caliche horizons. A resistant layer of caliche called the "caprock" generally occurs at the top of the Ogallala Formation. An unconfined aquifer in the sands of the lower Ogallala is the principal source of groundwater in the southern high plains region and is the primary source of potable water for Pantex Plant and Amarillo. In the vicinity of Pantex Plant, this aquifer lies approximately 350 to 425 ft below land surface.
In the upper part of the Ogallala Formation is a discontinuous zone of low-permeability, fine-grained material that acts as a relatively impermeable barrier to the vertical flow of infiltrating water. This zone apparently causes water to perch above the main Ogallala aquifer across most of Pantex Plant. Figure 2.2-3 is a geologic cross section across Pantex Plant showing the position of the water table in both the perched and main Ogallala aquifers.
The base of the Ogallala is an irregular surface that represents the pre-Ogallala topography, which was influenced by the dissolution of underlying Permian salts. Consequently, the depth to the base of the Ogallala Formation varies across Pantex Plant from approximately 400 ft below the southwest corner of the plant to nearly 800 ft below the northeast corner of the facility. The thickness of the Ogallala Formation in the vicinity of Pantex Plant ranges from approximately 325 to 725 ft, increasing from southwest to northeast (ANL, 1994).
Triassic strata of the Lower Dockum Group underlie the Ogallala Formation at Pantex Plant. These rocks consist of shale, clayey siltstone, and sandstone. The Lower Dockum Group is <100 ft thick beneath Pantex Plant and is underlain by Permian rocks. Where the Dockum Group strata are absent, the Ogallala Formation lies uncomformably on the Permian strata, comprising mudstone, anhydrite, or salt beds with relatively low permeability (Native, 1988). The lateral extent, thickness, and hydraulic characteristics of the Dockum Group formations beneath Pantex Plant have not been determined. Little lithologic information is available for the Dockum Group strata beneath Pantex Plant.
The Dockum Group formations provide an additional source of groundwater in the area. Several wells south of Pantex Plant have been completed in the Dockum Group aquifer and are used for domestic and livestock purposes but, in general, the aquifer has little economic importance for the region.
2.2.5.2 Soils
The system of soil classification used by the National Cooperative Soil Survey has six categories, beginning with the broadest category (order) and ending with the most definitive category (series). The series category consists of soils that have similar horizons in profile. A soil series horizon is identified by similarity in color, texture, structure, and mineral and chemical composition. Similar soil series are grouped into the next broader category, the association.
The Pullman series is the most common soil type in the area covering about four-fifths of the more level southern high plains portions of Carson County. Pullman soil is a finely textured silty clay loam that is easily eroded. Randall clay and several other soils occupy the playas and make up the remaining 20% of the southern high plains area within Carson County. Pullman soil and these other soil series are grouped into the Pullman-Randall association. Randall clay soil forms in the low playa bottoms. A variety of soil series are found on the slopes of the playa basins, including Pep and Estacado clay loams, Lazbuddie clay, Lofton silty clay loam, and some sloping Pullman soils (which are distinguishable from the Pullman soils on the flat interplaya areas) (see Figure 2.2-4). The soil classification for these soils has changed since the publication of the Soil Survey of Carson County (USDA, 1962) and that these soil names reflect the new classification. An update to the soil survey is being conducted but has not been published to date.
2.2.5.3 Principal Hydrogeologic Units
There are two principal water-bearing units beneath Pantex Plant and the adjacent areas. These are the Ogallala aquifer and the underlying Dockum Group aquifer. The vadose, or unsaturated zone, consists of up to 460 ft of sediments that lie between the land surface and the Ogallala aquifer. The general direction of soil water flow in the unsaturated zone is controlled by gravity and differential moisture content and is vertically downward until the water reaches a barrier (zone of low permeability) or the Ogallala water table.
A perched water zone lies approximately 100 ft above the main zone of saturation in the middle of the Ogallala Formation. The perched zone is fairly continuous across the eastern half of the Pantex Plant area. The saturated thickness in the perched aquifer varies from 0 to 100 ft thick. The lateral extent of this perched zone is not yet fully defined, and characterization of the lateral extent is ongoing.
The main Ogallala aquifer lies below the perched zone. The Ogallala aquifer is defined as the basal water-saturated portion of the Ogallala Formation and is the principal water supply of the southern high plains. It is an unconfined aquifer that can yield 700 to 1,200 gal/min of high-quality water to the wells in the Pantex Plant area (M&H, 1993). During the 1950s, the normal direction of groundwater flow in the Ogallala aquifer beneath Pantex Plant was to the east. Subsequent pumpage from the aquifer from the Amarillo water wellfield created a water table depression northeast of Pantex Plant. The direction of groundwater flow in the main Ogallala aquifer below Pantex Plant is from southwest to northeast.
The Dockum Group aquifer lies under the Ogallala at Pantex Plant and south of the Plant. Water contained in the sandstone layers within the Lower Dockum Group rocks supplies domestic and livestock wells south and southeast of the Plant. The Dockum aquifer may be semiconfined with respect to the overlying Ogallala aquifer because of lateral variations in the Ogallala and shale layers within the Dockum. No detailed information is available on the potentiometric surface of the Dockum aquifer for the Pantex Plant area, but the direction of the groundwater flow may be to the southwest along the slope of Triassic beds.
2.2.6.1 Agricultural Land
Most land at Pantex Plant that is not used for the Plant's mission-related operations is used as a security buffer and maintained in agricultural crops. The agricultural activities consist of grazing cattle and growing crops. Agricultural land within the Pantex Plant boundary (approximately 8,070 acres) is managed by the Texas Tech Research Farm through an agreement with the DOE (DOE, 1983). In addition, the research farm itself consists of approximately 1,000 acres of farmland and a former feedlot located southwest of the Pantex Plant boundary near Playa 5. The DOE-owned land surrounding Pantex Lake (1,080 acres) also is leased out for ranching.
A large portion of Pantex Plant is used for grazing cattle. Cow and calf operations are the typical ranching operations in this area (BMI/M&H, 1994). At the Plant, cattle are moved to different areas depending on the availability of forage. Grazing often occurs in the playas. Typically, grazing of the playas begins in late June or early July and continues until the forage is depleted, which typically occurs in late September.
Cow and calf operations are maintained in the Texas panhandle on large ranches. About 23,000 head of beef cattle graze on more than 92 ranches within a 5-mi radius of the Pantex Plant.. About nine large-scale dairies are located within a 50-mi radius of the Plant. Approximately 84,600 lb of milk per day are produced from the nearly 1,700 dairy cows at these dairies.
In addition to grazing operations, some areas of Pantex Plant are cultivated. This farmland usually is planted under dryland condition or with limited irrigation. In some cases, crops are rotated between winter wheat, fallow fields, and grain sorghum. Irrigation water, when used, is taken either from the Ogallala aquifer or, less frequently, from the playas (BMI/M&H, 1994). Both irrigated and dryland hard red winter wheat is planted in early September. Drought-resistant grain sorghum is grown under limited irrigation or dryland conditions (DOE, 1983). The winter wheat often is grazed by the cattle in the early growth stages (November to March); after March, the cattle are removed and the wheat is allowed to mature. The major soil type, the Pullman series, is finely textured and easily eroded, requiring careful cropping practices to minimize wind loss and sheet erosion under fallow conditions (DOE, 1983).
Both dryland farming and irrigated farming are conducted on farms in the areas around Pantex Plant. Wheat, oats, barley, and sorghum are the major commercial crops grown in the area. About 42,000 acres are in commercial crop production within a 5-mi radius of the Plant. An agricultural research station maintained by Texas Tech is directly adjacent to and co-located with Pantex Plant.
There are approximately
2.2.6.2 Human Populations
The work force at Pantex Plant consists of approximately 3,400 technical and support personnel, many of whom live in the Amarillo area. Rural housing development increases several miles to the south and southwest of Pantex Plant, in the direction of Amarillo.
Within a 5-mi radius of Pantex Plant, there are approximately 200 housing units, excluding 500 units at Highland Park Village and the Texas State Technical College (TSTC). Approximately 2,000 people reside in this 5-mi radius, including approximately 1,500 residents of Highland Park Village and TSTC. The closest community to the Plant is Panhandle, Texas (1990 population of 2,353), located about 8 mi to the east. Other small towns in the area include Fritch, White Deer, Claude, and Borger (Bureau of the Census, 1990).
All of these towns have agricultural- or petrochemical-based economies. Within a 50-mi radius of Pantex Plant, the population reaches approximately 240,000 persons (1990 population), primarily due to the 157,600 residents of Amarillo. The next largest populated area is Pampa, Texas, located 35 mi northeast of Pantex Plant, with a population of approximately 19,900. Because the local economy is influenced most significantly by agriculture and related industries, the population in the area is expected to have a moderate growth rate. There are no significant seasonal or transient populations located in the Pantex Plant area.
Within a 50-mi radius of the Pantex Plant site, there are 137 school facilities with a total enrollment of approximately 54,000. These include both accredited and nonaccredited schools serving students from prekindergarten through grade 12 in 25 school districts. Within a 5-mi radius, there is an elementary and high school (southwest of Pantex Plant) with an annual enrollment of approximately 650 students. The Potter County Correctional Facility is located approximately 3 mi southwest of Pantex Plant.
The Lake Meredith National Recreational Area (20 mi north) is used by more than 1 million visitors each year. Other major recreational areas in the region surrounding Pantex Plant include the Greenbelt Reservoir (40 mi southeast), Palo Duro Canyon State Park (20 mi south), MacKenzie Reservoir 48 mi south), Buffalo Lake National Wildlife Refuge (35 mi southwest), and the Alibates Flint Quarries National Monument (15 mi north) (Burns and McDonnell, 1991).
2.2.7.1 Wetlands and Wildlife
When flooded with runoff from precipitation, the playa basins scattered over the landscape provide a suitable environment for aquatic insects. These temporary ponds also provide resting, feeding, and nesting habitats for migratory waterfowl and shorebirds. Lake Meredith contains substantial populations of white bass, walleye, white crappie, carp, catfish, and large- and smallmouth bass. These populations vary significantly in response to changes in fishing limits.
Quail and pheasant are found in abundance in areas surrounding the Pantex Plant. Quail hunting is an important activity in this region. It is possible to find pheasants wherever farming is conducted, although the heaviest concentrations are found north and east of the Plant.
The big game found in surrounding areas includes white-tailed deer, mule deer, and pronghorn antelope. The mule deer population has been expanding in recent years. This species may occur anywhere in the central and eastern Panhandle where there is suitable habitat (e.g., river and creek drainages with dense brush). The heaviest concentration of mule deer occurs predominantly northwest and west of Pantex Plant. Antelope are found primarily north and west of Pantex Plant.
2.2.7.2 Threatened and Endangered Species
Threatened and endangered species are those species that are protected or being considered for protection under federal or state laws. Several protected or candidate threatened and endangered species have been documented as occurring on Pantex Plant, and several others have the potential to occur given their range and habitat requirements. Five protected or candidate threatened and endangered animal species were observed on the Pantex Plant site between 1992 and 1994 (Allison, 1994; BMI/M&H, 1994). In the past, two other species were reported to have been observed there.
Currently, the only federally and state-listed endangered species known to inhabit Pantex Plant for an extended period of time is the bald eagle (Short, 1994). The northern bald eagle is a winter resident of the high plains of Texas, and its winter habitat includes reservoirs, lakes, playas, rivers, and marshes. Wintering eagles may concentrate along various forks and tributaries of the Canadian and Red rivers and the assorted reservoirs and wetlands associated with these rivers. Wintering bald eagles may arrive in the high plains as early as October and migrate north from February through March. Therefore, the bald eagle is considered a winter resident and a spring and fall migrant in the area of Pantex Plant. During 1993, the bald eagle was observed on Pantex Plant foraging among the playas and prairie dog towns (BMI/M&H, 1994).
The Texas horned lizard, a federal Category 2 candidate species (Short, 1994) and a state threatened species (Texas Parks and Wildlife Department, 1993), is a resident species on Pantex Plant and was observed onsite in 1992 and 1993 (Burr, 1992; BMI/M&H, 1994). This species has been found on the uplands of the playas and in the more naturally vegetated areas of Pantex Plant. This species inhabits flat, open, generally dry country, including desert, shrubland, and grassland habitats. A fast runner, it seeks shelter under rocks, among low-growing vegetation, and in burrows of other animals. It is also capable of burying itself in loose soil. The horned lizard feeds primarily on ants and is often seen near an ant trail or mound. It usually is seen only on warm or hot days during late spring and summer. Hibernation begins in September or October and continues to April or May (Short, 1994).
The white-faced ibis, also a federal Category 2 candidate species and a state threatened species, was observed onsite in 1993 (BMI/M&H, 1994), and in 1992, approximately 36 white-faced ibis were observed at Playa 2 between August 13 and September 18 (Burr, 1992). This heron-like wading bird occurs along the Texas Gulf coast and in the midwestern part of the United States. It can occur year-round in Texas, including during the breeding season. It inhabits wetlands, preferably marshes and sloughs, surrounded by low bushes and with emergent vegetation. It feeds primarily in freshwater on frogs, fishes, insects, invertebrates, and crustaceans (Short, 1994).
The ferruginous hawk is a resident species on Pantex Plant that was observed during 1992 and 1993 (Burr, 1992; BMI/M&H, 1994; Short, 1994). Burr (1992) noted that ferruginous hawks were observed in the Pantex Plant area at Pantex Lake, at Playa 1, and over the open fields between Playas 2 and 3, and that these hawks are expected to forage throughout the Pantex Plant area. These hawks appear to be more numerous in winter. This species is a federal Category 2 candidate species but is not listed by the state.
The whooping crane, ranked as endangered on both the federal and state lists, is considered a spring and fall migrant in the area of Pantex Plant (Short, 1994; Texas Parks and Wildlife Department, 1993). Whooping cranes may be encountered during migration in any county in north central Texas plus in several of the easternmost counties of the Texas panhandle. Autumn migration normally begins in mid-September, with most birds arriving on the wintering grounds at Aransas National Wildlife Refuge between late and mid-November. Spring migration occurs during March and April. Whooping cranes prefer isolated areas away from human activity for feeding and roosting, and utilize vegetated wetlands and wetlands adjacent to cropland along the migration route. Foods consumed usually include frogs, fish, plant tubers, crayfish, insects, and waste grains in harvested fields (Short, 1994). Seyffert (1994) reported that although only one confirmed sighting has been reported on the Pantex Plant site, the whooping crane has been found on several occasions on playa lakes in the vicinity of the Plant.
The swift fox, a federal Category 2 candidate species, is suspected to occur on the Pantex Plant site (Short, 1994). The swift fox was last sighted on the Pantex Plant site in 1970 (BMI/M&H, 1994). Potential dens of swift fox reportedly have been found near several of the playas (Cushing et al., 1993).
In addition to the species observed on the Pantex Plant site, several protected and candidate species have the potential to occur on the site given their range and habitat.
The peregrine falcon is considered a spring and fall migrant and may occur at Pantex Plant during migration (September through May) (Short, 1994). There are two subspecies of peregrines. The American peregrine falcon is listed as endangered on both the federal and state lists (Texas Parks and Wildlife Department, 1993). The Arctic peregrine falcon is listed as threatened on both the federal and state lists (Texas Parks and Wildlife Department, 1993). Peregrine falcons usually frequent large rivers and reservoirs and/or cliffs and bluffs. They prey on a variety of small birds and small mammals, swooping down on prey at high speeds (Short, 1994).
The interior least tern is considered a possible spring and fall migrant in the area of Pantex Plant (Short, 1994), but has not been documented to occur onsite. The state and federal status of this species is endangered (Short, 1994; Texas Parks and Wildlife Department, 1993). The interior least tern is a state-wide migrant throughout Texas and nests on bare to sparsely vegetated river sandbars from May through August along the Red and Canadian rivers in north Texas (Short, 1994).
Five additional federal candidate species of birds were identified by Seyffert (1994) as potentially present on Pantex Plant but were not included in information received from the U.S. Fish and Wildlife Service. These included the black tern ( Category 2), the snowy plover (Category 2), the mountain plover (Category 1), Baird's sparrow (Category 2), and the loggerhead shrike (Category 2). The black tern is a common spring and fall migrant; the snowy plover, the mountain plover, and Baird's sparrow are all considered rare spring and fall migrants; and the loggerhead shrike is common as a migrant, uncommon as a year-round resident, and thought to nest on site (Seyffert, 1994; Allison, 1994).
2.2.7.3 Critical Habitats
No critical habitat for threatened and endangered species is located on or near Pantex Plant (Short, 1994).
The groundwater table in the Ogallala Formation beneath Pantex Plant has dropped rapidly since the 1940s. The large demands of the Amarillo area (including irrigation uses) are responsible for the drop in the water table. Pantex Plant production wells draw only a small amount of the groundwater reserves in relation to the water drawn for use in Amarillo and irrigation. From October 1992 through September 1993, Amarillo pumped about 8.58 billion gal of water from Lake Meredith, 0.84 billion gal from the southwest wellfield, and 5.84 billion gal from the Carson County Wellfield. During 1993, Pantex Plant pumped about 243 million gal from the Ogallala aquifer from onsite wells. Pantex Plant provided 62.2 million gal of the 243 million gal to Texas Tech for irrigation and personal consumption. The remaining 181 million gal was used for industrial and domestic purposes at the Plant (M&H, 1994).
Water for use at Pantex Plant is derived from five groundwater wells located in the northeast quadrant of the Plant property. The water distribution system includes seven water storage reservoirs whose functions include primary backup, elevated storage, and fire pump storage. The average distribution of water use at the Plant (based on a future estimate of 400 million gal/yr) is shown in Table 2.2-1 (DOE, 1983).
| Type of Water Use | Percentage | Gal (in millions) |
| Manufacturing and production process Plant operations resulting in sanitary effluent Use in steam plant Lawn and landscape irrigation Operation of cooling towers |
40 49 7 2 2 |
160 196 28 8 8 |
| Total | 100 | 400 |
Pantex Plant facilities also include a water treatment plant (to purify
water from the water-producing wells) and a sewage treatment plant. One
of the playas, located in the east-central part of the Plant site (Playa
1), is used as a retention basin for the Plant's treated sewage
effluents. Pantex Plant processes about 438,000 gal of sanitary
wastewater daily. Treated effluent that is not discharged to Playa 1 is
used by Texas Tech as irrigation water. In 1991, the average daily
discharge was 519,006 gal.
Irrigation water for local farming is provided by deep wells in the vicinity of Pantex Plant. Shallower wells (in the perched aquifer) generally produce poor quality water that, while suitable for livestock, has flow-rates insufficient for irrigation. Groundwater use is controlled by landowners or the local groundwater management districts.