Subsurface Geology of Hazardous Waste Injection Sands Near Geismar, Louisiana

Abstract

A third-party review of subsurface geology in the vicinity of Geismar, Louisiana, was conducted as part of the regulatory process for granting exemptions from “Land Ban” statutes that forbid injection of concentrated hydrochloric acid. Radial faults associated with a piercement salt dome displace both injection sands and isolation layers in Darrow Field (T10S R2E) and probably extend upward to the Gonzales aquifer, which is designated as an underground source of drinking water (USDW). A regional normal fault that extends from Laurel Ridge Field (T10S R13–14E) through Darrow Field also disrupts the injection interval. A concern is that these faults provide vertical pathways for transmission of hazardous waste out of the injection zone. The Upper B Sand, which receives hazardous waste from the Geismar Industrial Complex, is stratigraphically equivalent to an important fresh water sand in southeastern Louisiana, the Covington aquifer. Over most of the study area, the base of USDW is in the Gonzales aquifer, which appears to be isolated from the injection zone by the Confining layer. A mass transfer model (EQ6) for irreversible reaction of HCl with injection sands indicates that advective flow beyond the injection field is required for neutralization to occur.