Geohydrology of the proposed Waste Isolation Pilot Plant site, Los Medanos area, southeastern New Mexico
Geohydrologic data have been collected in the Los Medanos area at the U.S. Department of Energy 's proposed Waste Isolation Pilot Plant (WIPP) site in southeastern New Mexico since 1975 as part of an intensive study evaluating the feasibility of storing defense-associated nuclear wastes within the bedded salt of the Salado Formation of Permian age. Drilling and hydrologic testing have identified three principal water-producing zones above the salt, including the Rustler-Salado Formational contact and the Culebra and Magenta Dolomite Members of the Permian Rustler Formation. Below the bedded salt there is another water-bearing zone, the channel sandstones of the Bell Canyon formation of the Permian Delaware Mountain Group. Most data collected from 33 hydrologic test holes indicate that the water-bearing zones are characterized by low transmissivities and contain slightly saline to briny water. Data collected from drill-stem tests in the Bell Canyon Formation indicate the channel sandstones have hydraulic conductivities ranging from 0.02 to 0.36 feet per day grade vertically and laterally into siltstones and shales of very low permeability. The Rustler Formation contains the principal water-producing zones identified at the WIPP site. The Rustler-Salado formational contact has the least transmissivity, ranging from 0.00003 to 0.003 feet squared per day. The Culebra Dolomite is the most productive unit at the WIPP site with transmissivities ranging from 0.001 to 73 feet squared per day; the greater values result from fracturing in the dolomite created by dissolution of underlying halite. Minute vertical permeabilities prevent movement of water between hydrologic units. (USGS)