UMTRA Project water sampling and analysis plan, Falls City, Texas

Abstract

Surface remedial action will be completed at the Falls City, Texas, Uranium Mill Tailings Remedial Action Project site in the spring of 1994. Results of water sampling activity from 1989 to 1993 indicate that ground water contamination occurs primarily in the Deweesville/Conquista aquifer (the uppermost aquifer) and that the contamination migrates along four distinct contaminant plumes. Contaminated ground water from some wells in these regions has significantly elevated levels of aluminum, arsenic, cadmium, manganese, molybdenum, selenium, sulfate, and uranium. Contamination in the Dilworth aquifer was identified in monitor well 977 and in monitor well 833 at the southern edge of former tailings pile 4. There is no evidence that surface water quality in Tordilla and Scared Dog Creeks is impacted by tailings seepage. The following water sampling activities are planned for calendar year 1994: (1) Ground water sampling from 15 monitor wells to monitor the migration of the four major contaminant plumes within the Deweesville/Conquista aquifer. (2) Ground water sampling from five monitor wells to monitor contaminated and background ground water quality conditions in the Dilworth aquifer. Because of disposal cell construction activities, all plume monitor wells screened in the Dilworth aquifer were abandoned. No surface water locations are proposed for sampling. The monitor well locations provide a representative distribution of sampling points to characterize ground water quality and ground water flow conditions in the Deweesville/Conquista aquifer downgradient of the disposal cell. The list of analytes has been modified with time to reflect constituents currently related to uranium processing activities and natural uranium mineralization. Water sampling is normally conducted biannually in late summer and midwinter.