The Jackpile Uranium Mine, which is on the Pueblo of Laguna in northwestern New Mexico, was operated from 1953 to 1980. The mine and facilities have affected 3,141 acres of land, and about 2,656 acres were yet to be reclaimed by late 1980. The intended use of the restored land is stock grazing. Fractured Dakota Sandstone and Mancos Shale of Cretaceous age overlie the Jackpile sandstone and a 200-ft-thick tight mudstone unit of the Brushy Basin Member underlies the Jackpile. The hydraulic conductivity of the Jackpile sandstone probably is about 0.3 ft/day. The small storage coefficients determined from three aquifer tests indicate that the Jackpile sandstone is a confined hydrologic system throughout much of the mine area. Sediment from the Rio Paguate has nearly filled the Paguate Reservoir near Laguna since its construction in 1940. The mean concentrations of uranium, Ra-226, and other trace elements generally were less than permissible limits established in national drinking water regulations or New Mexico State groundwater regulations. No individual surface water samples collected upstream from the mine contained concentrations of Ra-226 in excess of the permissible limits. Ra-226 concentrations in many individual samples collected from the Rio Paguate from near the mouth of the Rio Moquino to the sampling sites along the downstream reach of the Rio Paguate, however, exceeded the recommended permissible concentration of Ra-226 for public drinking water supplies. Concentrations in surface water apparently are changed by groundwater inflow near the confluence of the two streams. The altitude of the water tables in the backfill of the pits will be controlled partly by the water level in the Rio Paguate. Other factors controlling the altitudes of the water tables are the recharge rate to the backfill and the hydraulic conductivities of the backfill, alluvium, Jackpile sandstone, and mudstone unit of the Brushy Basin Member. After reclamation, most of the shallow groundwater probably will discharge to the natural stream channels draining the mine area. Groundwater quality may be monitored as: (1) ' Limited monitoring, ' in which only the change in water quality is determined as the groundwater flows from the mine; or (2) ' thorough monitoring, ' in which specific sources of possible contaminants are described. (Author 's Abstract)