Applied forensic investigation of elevated arsenic levels in the Central Texas Trinity Aquifer system.

A recent change in EPA regulation lowered the maximum contaminate limit (MCL) of arsenic in drinking water from 50 to 10 μg/l. Lowering the MCL has put numerous water systems in Texas over the limit. An arsenic “hot spot” is located in parts of Falls, Hill, Limestone, and McLennan counties and is an issue for suppliers. All suppliers having arsenic issues in this "hot spot" produce water from the Hosston Member of the Trinity Aquifer. Because the Trinity Aquifer is a deep, confined aquifer, arsenic is presumed to occur naturally. This study incorporates chemical analysis of raw groundwater, entry point water, geophysical well logs, and cuttings from wells in an attempt to determine the (1) distribution, (2) source, (3) environment of occurrence, and (4) potential stresses to the aquifer which would cause elevated arsenic levels.