ABSTRACT

Some hydrocarbon exploration and production (E & P) wastes are disposed of in clay-lined earthen pits at centralized and commercial drilling-fluid disposal sites (CCDD sites). A developing Texas and Louisiana database includes over 150 active and inactive sites. Most active regulated sites accept water-based (<3,500 mg/ L chloride) fluids. However, hydrocarbons and brackish-to-saline groundwater are frequently present. Abandoned sites are a state's responsibility for evaluating and remediating, although these sites are generally poorly documented. Better-documented sites may provide analogs for abandoned sites. Three Louisiana and Texas sites exemplify a range of CCDD contaminant and groundwater-level characteristics.

At a St. Mary's Parish, Louisiana, site, groundwater chloride exceeding 2,000 mg/L is distributed in southeast- and northwest-trending plumes, which maintain their extent while concentration levels vary temporally.

At an Iberia Parish, Louisiana, site, plumes locally exceed 600 mg/L chloride and vary temporally between southerly and easterly trends. Chlorides are episodically flushed (<50 mg/L) from the site. Groundwater mounding occurs centrally at the site, which is a typical situation at many sites. Groundwater mounding suggests that some pits focus recharge. Focused recharge may carry potentially contaminated water to shallow aquifers.

At a Matagorda County, Texas, site, sludge constituents include non-uniformly distributed chloride, hydrocarbons, and arsenic. Chloride distributions in outwash areas provide a model for overflow through breached berms. Site documentation is unusual because constituent levels at specific sample locations are noted. Pre-analysis compositing of samples is typical of other site data, although compositing masks local constituent concentrations.