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Substantial quantities of water are being pumped from the Morrison Formation of Late Jurassic age in uranium mines in the Grants mineral belt in northwestern New Mexico. The water often contains unacceptable amounts of dissolved uranium, radium, iron, and selenium and suspended solids, but with treatment it can be made suitable for municipal and industrial purposes. Water salvaged from current and projected mining operations constitutes the most readily available water in this otherwise water-deficient area. Introduction Large quantities of water will be required by the coal-gasification and coal-burning electric powerplants planned for installation in northwestern New Mexico. The population of nearby communities is expected to increase significantly as the economy expands. Therefore, the demand for potable water will increase. Obtaining adequate supplies of potable ground water to meet even the existing demand is difficult, or, in many instances, impossible. The city of Gallup, in particular, has had great difficulty in providing an adequate supply of good-quality ground water for its municipal water system (Hiss, 1975, p. 13; City of Gallup, 1977, p. 3-4). The San Juan River and Rio Grande are the nearest reliable sources of large quantities of surface water. Transportation of surface water to areas of need would be more expensive generally than development of whatever local ground water might be available. Ownership of the land (surface and subsurface) and ownership, control, and (or) regulation of both ground and surface water often further complicate development and use of existing resources. Uranium mining New Mexico leads the nation in producing uranium concentrates and, perhaps of more importance, has about one-half of the undeveloped reserves of this valuable commodity (Fitch, 1974, p. 82). Most of the uranium mined to date and nearly all of the proven reserves occur in the Westwater Canyon Member of the Morrison Formation of Jurassic age in the Grants mineral belt (fig. 1). Production from most of the existing mines and those that will be developed in the future is and will be from depths well below the potentiometric surface of the Morrison Formation. During the mining, "long-holes" are drilled at the end of newly driven stopes, haulageways, or drifts to explore for and define the ore body and to drain the ground water from the rock. Removal of the water from the sandstone facilitates stoping and greatly increases the strength of the rock (Gay, 1963, p. 245-246; Hohne, 1963, p. 247). Eventually the network of mines will function as a vast underground collection system. Water must be pumped from these mines continuously in order to keep the various tunnels and shafts dry. The extent of Indian and Federal Land under lease is shown in figure 1. Although similar information is not available for State and private lands, the lease activity does reflect industry's interest in uranium mining in the Grants mineral belt. Church Rock mining district One abandoned mine and several producing uranium mines are located in the Church Rock mining district northeast of Gallup. The proximity of the mines to water-deficient Gallup enhances the potential for salvaging waste water from these mines for municipal use a course of action this city is now evaluating (Hiss, 1975, p. 112, 119; City of Gallup, 1977). Ownership and availability of the waste water are uncertain and must be resolved before the water can be put to beneficial use (Hiss, 1975, p. 66, 113, 120; City of Gallup, 1977, p. 7-10). Approximately 3,000 gpm (190 1/s) of ground water was being pumped in November 1973 from the Morrison Formation at two uranium mines in sec. 35, T. 17 N., R. 16 W., about 12 miles (20 km) northeast of Gallup in the Church Rock mining district (Hiss, 1975, p. 62, table 2). The discharge rate has subsequently increased to approximately 4,400 gpm (276 1/s). Further increases in waste-water production to more than 10,000 gpm (630 1/s) within a few years are predicted as new mines are opened (City of Gallup, 1977, p. 5, 8). The water generally contains less than 400 mg/1 dissolved solids; sodium and bicarbonate are the most abundant constituents. Except for the dissolved uranium, radium, iron, and selenium, the waste water contains less dissolved solids than the water now produced from the Cretaceous aquifers near Gallup (table 1, this report; City of Gallup, 1977, table 2). The waste water now is pumped to the land surface and into settling ponds where it is treated with barium chloride as a flocculating agent to remove suspended solids; this procedure simultaneously lowers the radium and uranium content (City of Gallup, 1977, p. 6). After most of the suspended particulate material has precipitated, the water is allowed to flow from the ponds into formerly dry arroyos that are tributaries of the Puerco River. The United Nuclear Corp. Northeast Church Rock Mine, an abandoned uranium mine, also completed in the Westwater Canyon Member, is located about 8 miles (15 km) northeast of Gallup near a paved road, a natural gas pipeline right-of-way, and high-voltage electrical power lines. Substantial quantities of water might also be produced from this abandoned mine for use by the City of Gallup if the rights to this resource could be obtained. Some of the waste water from the Church Rock mines will be used in a mill to be constructed near the producing uranium mines. Reportedly, large amounts of salvaged waste water will also be used in a coal-fired electric generating plan to be built on the Navajo Reservation. Behavior of potentiometric surface. Periodic measurements of the water level in the shaft of the Northeast Church Rock Mine were made for several years by personnel from United Nuclear Corp. Subsequently, a continuous water-level recording instrument was installed by the U.S. Geological Survey in order to monitor the long-term effects of pumping on the aquifer (fig. 2). The head in the Westwater Canyon aquifer has declined at a rate of approximately 1.85 ft/mo (0.56 m/mo) indicating the reduction in the hydraulic head caused by dewatering of the active mines in the Church Rock mining district. Ambrosia Lake mining district Uranium is now being mined from the Westwater Canyon Member of the Morrison Formation within the zone of saturation in the Ambrosia Lake mining district.. Millions and perhaps billions of gallons of waste water are discharged yearly as the mines are dewatered (Cooper and John, 1968, p. 38-42). Production of waste water can be expected to increase as the intensity of the mining increases and as new mines are developed. A small fraction of the water pumped from the mines is used in the uranium ore processing mills. Most of the waste water is discharged at the land surface and infiltrates or evaporates. Part of the water is channeled into formerly dry arroyos that carry the effluent southward out of the Ambrosia Lake area and into San Mateo Creek, a tributary of the Rio San Jose (Cooper and John, 1968, p. 40). Generally, the ground water pumped from the uranium mines is only slightly radioactive but it occasionally exceeds the recommended limit for safe drinking water (Cooper and John, 1968, p.28, 40-42). As mining proceeds, however, the quality of water involved deteriorates rapidly and, as a consequence, usually does not meet safe drinking standards. The total of dissolved constituents found in water produced from the Westwater Canyon aquifer in the Ambrosia Lake mining district ranges from less than 300 to more than 1,400 mg/1. Most of the water sampled by Cooper and John (1968, table 3) contained less than 700 mg/1 of total dissolved solids. Smith Lake mining district Public Service Company of New Mexico has proposed to construct a 2,000-megawatt power plant near Bisti. Water pumped from uranium mines to be located near Crownpoint, approximately 30 miles (50 km) to the south, reportedly may be used in the electric generating plant. Conclusions Reports from industry sources indicate that reserves in the Grants mineral belt will sustain uranium mining for many years. The large quantities of water pumped from the mines as they are dewatered now constitute a supply that could be salvaged and used beneficially after treatment to remove undesirable dissolved and suspended constituents. After mining ceases, the abandoned mines will comprise a large underground collection system. High-capacity pumps could then be installed in the abandoned shafts and water pumped from the mines as needed. However, this resource is finite and the long-term effects of dewatering will determine availability of water and economics of recovery at any particular location. Ownership of the land surface, the subsurface, water and (or) water rights, and the legal control of the use of water are factors that will influence use of this supply of ground water.

Uranium mine waste water: potential source of ground water in northwestern New Mexico