Census Statistical Characterization of Soil and Water Quality at Abandoned and Other Centralized and Commerical Driling-Fluid Disposal Sites in Louisiana, New Mexico, Oklahoma, and Texas

Commercial and centralized drilling-fluid disposal (CCDD) sites receive a portion of spent drilling fluids for disposal from oil and gas exploration and production (E&P) operations. Many older and some abandoned sites may have operated under less stringent regulations than are currently enforced. This study provides a census, compilation, and summary of information on active, inactive, and abandoned CCDD sites in Louisiana, New Mexico, Oklahoma, and Texas, intended as a basis for supporting State-funded assessment and remediation of abandoned sites. Closure of abandoned CCDD sites is within the jurisdiction of State regulatory agencies. Sources of data used in this study on abandoned CCDD sites mainly are permit files at State regulatory agencies. Active and inactive sites were included because data on abandoned sites are sparse. Onsite reserve pits at individual wells for disposal of spent drilling fluid are not part of this study.

Of 287 CCDD sites in the four States for which we compiled data, 34 had been abandoned whereas 54 were active and 199 were inactive as of January 2002. Most were disposal-pit facilities; five percent were land treatment facilities. A typical disposal-pit facility has fewer than 3 disposal pits or cells, which have a median size of approximately 2 acres each. Data from well-documented sites may be used to predict some conditions at abandoned sites; older abandoned sites might have outlier concentrations for some metal and organic constituents. Groundwater at a significant number of sites had an average chloride concentration that exceeded nonactionable secondary drinking water standard of 250 mg/L, or a total dissolved solids content of > 10,000 mg/L, the limiting definition for underground sources of drinking water source, or both. Background data were lacking, however, so we did not determine whether these concentrations in groundwater reflected site operations.

Site remediation has not been found necessary to date for most abandoned CCDD sites; site assessments and remedial feasibility studies are ongoing in each State. Remediation alternatives addressed physical hazards and potential for groundwater transport of dissolved salt and petroleum hydrocarbons that might be leached from wastes. Remediation options included excavation of wastes and contaminated adjacent soils followed by removal to permitted disposal facilities or land farming if sufficient on-site area were available.