LEACHING OF HAZARDOUS SUBSTANCES FROM RETORTED OIL SHALE DURING HIGH TEMPERATURE WATER FLUSHING

The reclamation plan proposed for spent oil shale following the application of Shell Frontier Oil & Gas Inc.'s In Situ Conversion Process (ICP) involves water flushing in order to cool the spent rock and remove labile organic and inorganic pollutants. This approach has the potential to enhance the removal of volatile and semi-volatile organic compounds and ionic species from the spent rock relative to flushing operations conducted at ambient temperatures. The improved removal of hazardous substances is the result of several factors, including: the production of steam increasing volatilization of organics; a reduction in water polarity at subcritical conditions solubilizing organics; and an increase in the rate of dissolution of ionic species. However, there do not seem to be any publically available data on the effectiveness of this process for in situ oil shale retort remediation. We have conducted a series of post-pyrolysis leaching experiments using oil shales from the Mahogany zone of the Eocene Green River Formation collected in the Piceance Basin. Spent oil shale retorted using a laboratory procedure designed to mimic the ICP was heated following the addition of water. Aqueous leachates were collected and analyzed to determine basic water quality criteria and concentrations of a range of byproducts of environmental concern. The results were assessed relative to regulatory limits and contrasted with results from room temperature leaching experiments. Differences between the field and laboratory application of this approach to spent shale reclamation will be discussed.