Evaluation of Groundwater Methodologies in the Tucson Copper Mining District

Abstract

The Upper Santa Cruz Basin Mines Task Force implemented a two year groundwater monitoring program in response to recommendations of an earlier investigation. The work program included monitoring several copper mines' tailing ponds and wells 15-20 miles south of Tucson. ASARCO mine was monitored to determine the source of high sulfates and TOS in the groundwater in the vicinity of the ASARCO ponds. A network of twelve sampling sites was sampled quarterly to look at water quality trends over time. One additional monitor well was drilled at the base of ASARCO's newest pond. The Anamax groundwater monitoring program consisted of investigating changes in water levels and water quality in the vicinity of its two tailing ponds to determine the hydrologic impacts of the ponds. The Duval program consisted of a network of thirteen monitor and seven interceptor wells. It was designed to determine the effectiveness of the interceptor wells as a management practice for preventing migration of mineralized tailing pond seepage to downgradient areas. The programs are compared in relation to their relative merits and their effectiveness in determining the groundwater quality impacts of the tailings ponds.