A Case Study of the Effects of Oil Shale Operations on Surface and Groundwater Quality: I. Sources of Contamination and Hydrologic Controls on Water Composition

Abstract

AbstractA study was undertaken to determine the effects of the disposal and leaching of retorted shale and other wastes on the water quality of a local drainage at the Rifle Oil Shale Project. An estimated 200 000 t of retorted shale and 146 000 t of raw shale were disposed during a 35‐yr period at the site, located near Anvil Points, CO. Previous studies suggested that operations did not impact the site. However, this investigation revealed elevated salt concentrations in wells, seeps, and surface waters downstream of the site. This investigation included a detailed survey of the potential contaminant and water sources at the site and measurement of inorganic and organic constituents in surface and groundwaters as a function of proximity to the disposal areas and hydrologic factors in the watershed. Sources of the salts were unlined evaporation ponds, subsoils leached by waters from leaking sanitary water system, and leachates from the raw and retorted shale piles, which also serve as artificial water recharge areas. These sources had not been previously detected because prior investigations did not take into account distinct spatial and diurnal fluctuations in flow rate in the surface waters, which alternately diluted and concentrated contaminants contributed by groundwater recharge. Fluctuations in flow rate were shown to result from daily meteorological effects on snowmelt (December–March) and transpiration by vegetation in the watershed (June–December). Detailed assessments of these factors are required before the long‐term effects of an oil shale industry on the Colorado River Basin can be determined.