Minerals Beneficiation - Deep Well Construction for the Disposal of Uranium Mill Tailing Water by The Anaconda Co. at Grants, N. M. (MINING ENGINEERING, 1962, vol. 14, No. 7, p. 49)

A deep well injection system is used by The Anaconda Co. for the disposal of uranium mill tailing water near Grants, N. M. A 2511-ft hole was cored and tested through Triassic, Permian, and Pennsylvanian (?) sediments and bottomed in Precambrian granite gneiss. The disposal well was plugged back to 1830 ft and completed in 563 ft of sandstones in the Yeso formation. The reservoir sandstones contain water similar to the injected waste water, and are isolated from overlying fresh-water aquifers by an evaporite barrier zone. Mill tailing water is decanted, filtered, and introduced into the well by gravity at an average rate of 400 gpm. The reservoir has a life expectancy of 10 years. The Anaconda Co. began uranium milling operations near Grants, N. M. in 1953 with a small mill that processed limestone ores. A larger second mill was built in 1955 to treat sandstone ores. In 1956 it became apparent that a large tailing pond would be required to contain the increased discharge of mill waste water. Research was begun on supplementary methods of disposal by which a minimal pond size could be maintained to avert excessive seepage losses. An intensive sampling program was begun to monitor the fresh-water wells in the area. The original limestone mill ceased operation in 1959. The present mill treats sandstone ores by sulfuric acid leach and a resin-in-pulp ion exchange recovery circuit that uses chloride elution. Process waste water is discharged to a tailing pond where, after evaporation losses, an annual average of about 400 gpm are available for injection into the disposal well. The waste water is a mildly acid solution that contains large amounts of manganese, iron, and the sulfate and chloride salts of sodium, calcium, and magnesium. It is a low-level radioactive fluid that contains small amounts of Uranium-natural, Thorium-230, and Radium-226. The average chemical and radioactive analyses of the waste water injected into the disposal well are shown in Column B of Table I. Disposal of the excess mill waste water by deep well injection was investigated after extensive research had proved that alternate methods were not satisfactory. A study of the regional geology and hydrology indicated that a disposal well was feasible, and a test well to basement rock was planned. Tentative plans for the test well and the results of the geologic and hydrologic studies were submitted to the New Mexico Dept. of Public Health, the New Mexico State Engineer's Office, the U.S. Atomic