Ground water tailings pond monitoring in the upper Santa Cruz Basin mines task force special studies area was performed to determine the nature and extent of aquifer contamination from copper tailings pond recharge in the basin. A monitoring program for each of three mining areas (mines a, b, and d) was developed. Analyses of data show that recharge from mine a ponds caused increased hardness, sulfate, and total dissolved solids in local ground water. However, pumpage in the area has controlled most of the water's movement. Pond recharge from mine b led to similar conditions, and the degraed water is moving towards a local public-supply well. Pumpage from mine d interceptor wells is controlling some, but not all, of the movement of recharge seepage from ponds in that area. Recommendations are included in the report.