Assessment and control of water contamination associated with shale-oil extraction and processing

The Los Alamos National Laboratory's research on assessment and control of water contamination associated with oil shale operations is directed toward the identification of potential water contamination problems and the evaluation of alternative control strategies for controlling contaminants released into the surface and underground water systems from oil-shale-related sources. Laboratory assessment activities have focused on the mineralogy, trace element concentrations in solids, and leaching characteristics of raw and spent shales from field operations and laboratory-generated spent shales. Process parameters in modified in situ (MIS) retorting are extreme. Mineralogic characterization of field-generated spent shales indicate that carbonate decomposition and silication reactions occurred in Occidental Oil Shale, Inc., retort 3E at Logan Wash, Colorado. However, evaluation of leachate compositions and comparison with water quality criteria and Multi-Media Environmental Goals/Minimum Acute Toxicity Effluents indicate that several environmentally sensitive trace elements, including potassium, lithium, fluoride, vanadium, lead, boron, molybdenum, nickel, selenium, and arsenic are not rendered immobile by in situ processing and could be of environmental concern. These conclusions are verified by investigations of laboratory-generated spent shales. This report details the chemical, mineralogic, and solution behavior of major, minor, and trace elements in a variety of shale materials (spent shales from Occidental retort 3E at Logan Wash, raw shale from the Colony mine, and laboratory heat-treated shales generated from Colony mine raw shale). Control technology research activities have focused on the definition of control technology requirements based on assessment activities and the laboratory evaluation of alternative control strategies for mitigation of identified problems. Based on results obtained with Logan Wash materials, it appears that the overall impact of in situ processing on groundwater quality (leaching and aquifer bridging) may be less significant than previously believed. Most elements leached from MIS spent shales are already elevated in most groundwaters. Analysis indicates that solubility controls by major cations and anions will aid in mitigating water quality impacts. The exceptions include the trace elements vanadium, lead, and selenium. With respect to in situ retort leaching, process control and multistaged counterflow leaching are evaluated as alternative control strategies for mitigation of quality impacts. The results of these analyses are presented in this report.