The Monument Valley UMTRA Project site is on the Navajo Reservation in northeastern Arizona, about 15 miles (24 kilometers) south of Mexican Hat, Utah, and about 13 miles (21 kilometers) east of the scenic Monument Valley tribal park. Comb Ridge, the most prominent topographic feature, is east of the site. The Monument Valley site is in a sparsely populated area. The nearest town is Dennehotso, about 5 miles (8 kilometers) south. The climate is arid; average annual precipitation is 6.4 inches (16 centimeters), and an average annual snowfall is 3.3 inches (8.4 centimeters). The region is characterized by a desert shrub habitat with scattered junipers growing on higher terrain and rocky areas. There are no known threatened or endangered species at or near the site.

The tailings site consisted of two tailings piles, windblown-contaminated soil, and piles of debris. The total volume of contaminated material at the site was 942,000 cubic yards (720,000 cubic meters) on 83 acres (34 hectares). All the contaminated material has been moved to the Mexican Hat, Utah, disposal cell 17 road miles (27 kilometers) to the north, and surface remedial action was completed in May 1994.

The three main aquifers at the site are, in descending order, the alluvial, Shinarump, and De Chelly aquifers. Depth to ground water in the alluvial aquifer ranges from a few feet in Cane Valley Wash to slightly more than 60 feet (18 meters) downgradient from the site. This ground water is recharged by occasional infiltration from precipitation and upward leakage from the semiconfined Shinarump. Depth to ground water in the Shinarump ranges from 7 to 50 feet (2 to 15 meters) below ground surface. The De Chelly aquifer consists of fine-grained sandstone that is approximately 500 feet (150 meters) thick in the site area. Ground water in the De Chelly is present under artesian conditions in three wells south and east of the site and may be unconfined in areas west of the site, where the maximum measured depth to ground water is 165 feet (50 meters).

Nitrate and uranium are the only site-related contaminants that exceed UMTRA Project maximum concentration limits in the alluvial aquifer. A nitrate plume with concentrations ranging from 44 to 1,030 mg/L extends approximately 4,500 feet (1,370 meters) north of the site. Uranium concentrations exceed the UMTRA standard of 0.044 mg/L at only one location, where 1997 data indicated a concentration of 0.069 mg/L. A similar uranium concentration is present in a well completed in the De Chelly at this location. No other constituents have been detected at concentrations above the maximum concentration limits in the De Chelly. The Shinarump aquifer has not been significantly affected by site-related contaminants. All constituents are below maximum concentration limits, although concentrations of ammonium, calcium, sulfate, and radium-226 exceed the upper limits of natural background.