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MONITORED NATURAL ATTENUATION AND RISK MANAGEMENT OF MTBE IN GROUND WATER (MONTEREY, CA)
Citation:
WILSON, J. T. AND B. E. WILSON. MONITORED NATURAL ATTENUATION AND RISK MANAGEMENT OF MTBE IN GROUND WATER (MONTEREY, CA). Presented at 5th International Battelle Conference, Monterey, CA, May 22 - 25, 2006.
Impact/Purpose:
To inform the public.
Description:
Monitored natural attenuation (as U.S. EPA defines the term) is a remedy, where natural processes bring the concentration of MTBE to an acceptable level in a reasonable period of time. The longevity of the plume is its critical property. The rate of attenuation is typically controlled by the rate of weathering of MTBE from residual gasoline. The course will present data from the literature on rates of attenuation typically seen at gasoline spill sites. Course participants will learn how to use non-parametric statistics to determine whether MTBE concentrations are attenuating over time. Participants will also learn how to use parametric statistics to estimate and compare the rate of attenuation, the rate of attenuation that is statistically significant at some level of confidence, and the rate of attenuation that is necessary to meet the clean up goal in a specified period of time. The course will provide data on the typical variability of long term monitoring data, and will discuss the amount of data that is necessary to detect natural attenuation at some level of statistical confidence. The goal of risk management is to prevent unacceptable impacts to receptors. The maximum size of the plume is its critical property. The course will present data from the literature on typical rates of attenuation of MTBE along a flow path in ground water. It will explain how the life cycle of a plume is controlled by the interaction between the rate of attenuation over time in the source and the rate of attenuation along the flow path. The size of MTBE plumes are largely controlled by natural anaerobic biodegradation. The course will briefly review the microbiology of anaerobic biodegradation of MTBE. The course will discuss the use of biogeochemical parameters to determine the footprint of a plume. Course participants will learn how to estimate the extent of biodegradation of MTBE in particular monitoring wells, and use the estimate to predict the ultimate size of the plume.