Site Investigation and Evaluation of Remediation Alternatives for the Post Oak Site, Lee County, Texas

The Bureau of Economic Geology (BEG) investigated the Post Oak site (RRC Site Code 03-0217) in Lee County, Texas, between June 1996 and August 1997. The site is a former sandstone quarry that was used for nonpermitted disposal of oil-field waste—specifically, spent drilling fluid. Disposal of wastes at the pit onsite occurred sometime before 1995, at which time the property owner reported the dumping to the Railroad Commission (RRC).

The scope of the BEG study was to determine the extent and composition of the waste materials, identify related impacted areas, determine the effects on groundwater quality, and evaluate risk-based options for site remediation. Constituents identified by BEG in waste materials at the site include petroleum hydrocarbons, chloride, and metals. This report presents (1) results of the site work and (2) remediation options for RRC to review before taking action at the site.

The waste materials, confined within the quarry walls and berms at the site, are underlain by sandstone, sands, and clays of the Wellborn Formation. There is no reported use of shallow or deep groundwater in the immediate area, which is served by a rural water-supply company. In general, the waste materials were found to be nonhazardous, with low levels of TPH that are below guidance levels and moderate concentrations of chloride that are below levels that might limit biodegradation. The wastes exhibited negligible TCLP leaching potentials for organic compounds and metals. Petroleum hydrocarbon concentration in the wastes averaged 0.096 percent below cleanup standards set by either RRC or TNRCC. Chloride concentrations averaged 2,500 mg/kg below the limit set for nonpermitted landfarming or burial. Metals detected in the waste materials did not exceed the regulatory limit for disposal of nonhazardous waste. Naphthalene was detected in waters and waste materials just at or below action levels, respectively.