Water-quality aspects of uranium mining and milling in New Mexico

Since 1977 the New Mexico Environmental Improvement Division has been implementing a systematic program for the regular collection of water-quality data relevant to the uranium mining and milling industry in New Mexico. This program has had two parts: (1) regular sampling of effluents discharged to ponds or to watercourses from all active uranium mills in the State and from all water-producing mines, whether active or under development; and (2) establishment and gradual expansion of a regional water-quality monitoring network in the Grants mineral belt (the region of principal uranium activity) to characterize hydraulic relationships and to trace contaminant migration within and between surface water and shallow ground-water flow systems. Based on information collected to date, some general observations are that the quality of water pumped from uranium mines varies considerably from area to area with much of it meeting most New Mexico ground-water standards and Federal NPDES (National Pollutant Discharge Elimination System) permit guidelines after treatment; that mill-tailings water is of much worse quality than mine water, containing concentrations of numerous contaminants far in excess of the above-mentioned standards; that surface waters and shallow ground-water systems in the Grants mineral belt usually are in hydraulic connection; that both surface and ground waters show some degradation downgradient from uranium industry areas, especially with respect to heavy metals; that the relative importance of various contaminant sources in contributing to this degradation is very difficult to determine at present; and that much more data is needed, especially data on the contribution of nonpoint sources