MTBE Diving Plume Study
In February 2001, Region 5 Underground Storage Tank Section received $100,000 to help study diving Methyl Tertiary Butyl Ether (MTBE) groundwater plumes from LUST sites. Region 5 collaborated with Dr. John Wilson & Steve Acree from ORD in Ada, Oklahoma and Jim Weaver with ORD in Athens, Georgia.
Three LUST sites which impacted the drinking water of communities were selected for this study. To study the effects of local land use upon plume movement, we attempted to find sites with varying surface conditions. Region 5 and ORD received valuable assistance from Steve Ales of WDNR, Jim Coger of MDEQ and Karl Kaiser & Gina Search of IEPA. They all assisted in site selection, contacts with the necessary local officials and in actual field work.
Site work was conducted during the summer months. Work included using the ORD direct-push rig to collect groundwater samples from discreet depths along a transect perpendicular to the contamination plume. Various samples were also collected from community water supply wells.
There are 3 main results from this project:
- The field data and ORD's analysis of the data
- A Site Characterization Methods Issue Paper
- Improvement upon an existing MTBE Diving Plume on-line calculator currently available at www.epa.gov/athens/onsite . Jim Weaver added a fate and transport component.
A preliminary assessment of the data indicates that well pumping plays an important role in plume behavior at all three sites. It appears that there is a downward push on the plume by rainwater recharge only at the Spring Green site, not detected at the other two sites. We have evidence that although the plume tends to follow the bottom of an upper confining layer, biodegradation is occurring along the top of the plume at all three sites. We are not yet sure which mechanism is the dominant form of biodegradation, but this will be the subject of further analysis. Another interesting development is the presence of tert butyl alcohol (MTBE degradation by product) only at the E. Alton site. This appears to be due to a greater anaerobic effect at this site. There are greater concentrations of Iron II compared to the other two sites.
The results of this study are scheduled to be published by the National Groundwater Association.
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