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Recent Findings in EPA’s Lead Scavengers Evaluation
Citation:
WILSON, J. T., C. J. ADAIR, AND H. WHITE. Recent Findings in EPA’s Lead Scavengers Evaluation. Presented at National Tanks Conference, Atlanta, GA, March 18 - 20, 2008.
Impact/Purpose:
Present information at a conference.
Description:
In response to continued concerns about the concentrations of 1,2-dibromoethane (EDB) in ground water from spills of leaded gasoline, OUST formed a Lead Scavengers Team with assistance from ASTSWMO. ASTSWMO and EPA Regions solicited participation from state agencies. Analysis was performed on 802 samples from 102 service stations or distribution terminals in 19 states. Results are now available from the survey. Concentrations of EDB were above the MCL in at least one monitoring well at 42% of the service station sites in the survey. EPA provided sample containers and shipping, wells were sampled for EDB during regular monitoring, and samples were shipped to the Kerr Center for analysis for EDB by Method 8011. The MCL for EDB is 0.05 µg/L. The concentration of EDB was above a detection limit of 0.01 µg/L at 55% of the stations. The concentration was greater than the MCL at 42% of the stations. The maximum concentration was above 1 µg/L at 25% of stations, above 50 µg/L at 10% of stations and above 100 µg/L at 6% of stations. The highest concentration determined in the survey was 982 µg/L. The prospects for long term persistence of EDB at a station should be related to the rate of weathering of EDB from residual gasoline, which should in turn depend on the flow of ground water past the gasoline. Detailed studies were conducted at 14 stations to compare the maximum concentrations of EDB to hydraulic conductivity as determined by slug testing, and to estimates of ground water seepage velocity. There was no statistically significant correlation of concentrations of EDB to hydraulic conductivity or seepage velocity. EDB is biodegradable under aerobic and anaerobic conditions. Concentrations of sulfate, methane, and nitrate, were determined in ground water as predictors of the prospects for biodegradation. There was no statistically significant correlation of concentrations of EDB to concentrations of sulfate, methane, and nitrate in ground water.