From November 1973 to October 1974, the U.S. Geological Survey drilled four deep test holes to supplement hydrologic and geophysical studies evaluating fresh ground water in the basins of westernmost Texas. For each test, samples of drill cuttings were collect·ed, borehole geophysical logs were run, and water samples were collected from specific zones.
The Leopold Guerra No. 1 test hole penetrated sand and gravel :o 1,100 feet (335m), and logs and water samples indicated fresh ground water to that depth. Below 1,100 feet (335m), the material probably has low permeability. The Clay Evans No. 1 test penetrated sand, gravel, and clay to 555 feet (169m), sand and thin volcanic flows to about 1,250 feet (381 m), and volcanic flows and tuffs to 2,006 feet (611 m). Logs and water samples indicated fresh ground \vater to about 1, 250 feet (381 m); below that, permeability is probably low. The Culberson County Airport test was drilled through sand, gravel, and clay to 1,145 feet (349m), conglomerate to 1,205 feet (367m), and the Lower Cretaceous Cox Sandstone to 1,306 feet (398m). Logs and water s~mples indicated fresh water in the alluvial fill and in the Cox Sandstone to about 1,265 feet (386m); below that depth, permeability is probably low. The Davis test was drilled through clay with some thin beds of sand and gravel containing fresh water to a depth of 2,012 feet (613 m).
Borehole temperature data indicated above-nonnal gradients in the Guerra and Culberson County Airport tests. Temperature gradients in the Evans and Davis tests were near normal.
