Wells across US threatened by MTBE contamination

Leaks of the gasoline additive MTBE from underground storage tanks could contaminate as many as 9,000 community water wells in 31 states US, according to recently published research.

Researchers from the US Geological Survey (USGS) and the Oregon Graduate Institute claim the research, published in the journal Environmental Science & Technology, shows that MTBE contamination of groundwater is present in the whole of the US.

The 9,000 wells identified in the study represent one-third of the community water supply wells in the 31 states. Approximately 90 million people in the US obtain a portion of their drinking water from such wells.

MTBE (methyl tert-butyl ether) is an oxygenate added to gasoline to make it burn more cleanly, thus reducing air pollution. However, MTBE has been shown to be a major contaminator of groundwater in high-oxygenate-use areas. MTBE is difficult to remove from water and can render drinking water unusable.

Earlier this week, the US EPA announced it would begin phasing out the use of MTBE in gasoline. The move follows the California Air Resources Board’s (CARB) decision last year to approve laws banning the additive from the beginning of 2003 (see related story).

The researchers estimate that around 250,000 storage tanks have released MTBE to the environment over the past 20 years causing significant groundwater contamination. Because MTBE is known to migrate long distances and is present in such large quantities, the researchers recommend the urgent completion of more detailed assessments of the 9,000 community wells.

The EPA’s proposed plan to reduce or eliminate the use of MTBE and to boost the use of alternatives such as ethanol takes the form of a legislative programme which will be presented to Congress. There will also be regulatory action by the EPA to eliminate MTBE in gasoline.

The legislative framework being sent to Congress includes three recommendations:

  • Congress should amend the Clean Air Act to provide the authority to reduce or eliminate the use of MTBE
  • as MTBE use is reduced or eliminated, Congress must protect air quality gains
  • Congress should promote growth in renewable fuels, such as ethanol, by replacing the existing oxygenate requirement in the Clean Air Act with a renewable fuel standard for all gasoline

In addition to the legislative framework, EPA has begun regulatory action to eliminate or phase out MTBE, under the Toxic Substances Control Act. This will give the EPA authority to ban, reduce or control the manufacture of chemical substances that pose an unreasonable risk to the public or the environment. EPA expects to issue a full proposal to ban or reduce MTBE within six months, after which more time will be allowed for analysis and public comment before a final action can be taken.

However, the authors of the study warn that even if MTBE is banned today, it will persist in the environment for at least a decade. “Because MTBE degrades slowly in groundwater, past MTBE-gasoline releases that reach groundwater will continue to threaten community water supply wells until at least the year 2010,” says USGS scientist John Zogorski, one of the study’s authors.

Zogorski adds that it could take Congress up to three years to come up with legislation to deal with the problem, and that the EPA’s analysis programme depends upon the completion of highly complex, initial studies. “The EPA will have to pull information together from a variety of sources,” Zogorski told edie. “For instance, we have to find areas in the US where MTBE is used at 1% by volume in gas and where they have done water quality tests so we can work out whether that’s an acceptable level. So far we haven’t found any of those areas. It’s going to take at least a year to pull the information together.”

The researchers also discovered that the more aggressively community water supply wells are pumped, the more likely it is that contamination from MTBE-gasoline releases will cause a problem.

Apart from California, several other US states plan to halt or reduce MTBE use. Maine has permission from the EPA to ban MTBE if it can find other ways of meeting air quality goals. Likewise, New Jersey has EPA approval to stop using extra MTBE in gasoline during the winter.

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