One exploratory hole, a test injection well, and nine monitor wells were constructed at the South Cross Bayou test-injection site between January 1973 and October 1975. At the test site, the first 125 feet below land surface is predominantly limestone and clay; from 125 to 3,280 feet it is mostly limestone and dolomite. Gypsum is also present below 1,260 feet. Wells within about a 1-mi radius of the test injection site were sampled and analyzed to provide water-quality background data prior to anticipated long-term injection at the test site. Locations of the wells sampled are shown, reported construction data are given, and the chemical analyses of water from these wells are tabulated. Chloride concentration of water from the wells near the test site ranged between 9.8 to 290 mg/L. Reported depth of these wells ranged from 25 to 302 ft. (Woodard-USGS)