New Mexico Geological Society Annual Spring Meeting — Abstracts

U.S. Environmental Protection Agency regulations, developed under the Resource Conservation and Recovery Act (RCRA), require a facility which treats, stores, and/or disposes of hazardous waste to obtain an operating permit. A thorough characterization of the site hydrogeology is required under RCRA to understand the environmental impact of facility operations. Controls on fluid movement in both the vadose zone and the uppermost aquifer must be determined prior to predicting the flow of potential contaminants released to the environment. WSTF began a detailed site hydrogeologic characterization in 1986 with geophysical and geologic surveys, a shallow soil boring project, and the installation of groundwater monitoring wells.

The presence of locally variable geomorphic features complicate fluid migration in the vadose zone. These surface variations and the presence of a shallow caliche zone reduce infiltration and aquifer rates and increase surface runoff.

Groundwater is located between 120 and 180 feet below WSTF in an unconfined aquifer. The aquifer transects three distinct geologic units: 1) The Camp Rice Formation (uppermost Santa Fe Group), 2) The Oligocene Orejon Andesite, and 3) Paleozoic Limestones of the Hueco Formation. The Oregon Andesite and Paleozoic carbonates typically have low matrix hydraulic conductivity and transmit water primarily through open fractures. Camp Rice sediments are believed to be highly variable in both lighology and hydraulic properties.

Small displacement, high angle faults act as primary structural control on groundwater-movement as a result of higher fluid transmitting capabilities. The direction of groundwater movement is west-southwest from WSTF into the Jornada del Muerto Basin.

Further hydrogeologic characterization will continue at WSTF with the information gathered during monitor well installation, seismic reflection surveys, aquifer testing, and groundwater modeling.