Every Move MTBE Makes
Finding a moving target can be difficult. Such is the case with chemicals from leaking underground storage tanks which can move in many ways into the ground and groundwater. In particular, MTBE, a petroleum-based chemical, can be difficult to identify because of the way it travels underground.
MTBE, or methyl tertiary butyl ether, is a water soluble gasoline additive that has contaminated groundwater in many parts of the United States when it leaks from underground storage tanks. In some cases, drinking water has been contaminated forcing communities to adopt expensive treatment alternatives.
Researchers in EPA's Office of Research and Development worked with EPA's regional office in Chicago and state environmental officials to improve the ability to identify and track MTBE leaks in groundwater. This research led to the development of new tools and computer models to predict the movement of MTBE from leaking tanks.
MTBE tends to travel further in aquifers than other chemicals. So it is subjected to more infiltration from rainwater. This causes it to "dive" into groundwater after it leaks from underground storage tanks, making it hard to detect.
Work on this problem began at a site in Long Island, New York, where MTBE contamination dropped as it moved beneath a gravel pit. Researchers then characterized the conditions that may indicate the presence of plume diving at three more study sites in the Midwest.
The research has assisted state and federal regulators with monitoring plans for underground storage tanks and provided support for cleanup of groundwater contaminated by the pollutant.
The research was met with skepticism at first, said Jim Weaver, EPA research hydrologist, but through perseverance and presentation of scientific data, the need to properly characterize diving plumes is now widely recognized as important to remediation.
These studies represented a cooperative effort among ORD, EPA's Regional Office in Chicago, and the environmental agencies of New York, Illinois, and Michigan.
Wilson, J.T., Ross, R.R., Acree, S. Site Characterization to Determine the Influence of Stratigraphy on a Diving Plume of MTBE in a Municipal Well Field. Ground Water Monitoring & Remediation, Volume 25, Issue 3, Page 93-102, Aug 2005, doi: 10.1111/j.1745-6592.2005.00031.x
Weaver, J.W. and Wilson, J.T. 2000, Diving Plumes, L.U.S.T.Line, New England Interstate Water Pollution Control Commission, 36, 12-15.