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Thursday, Dec 7, 2023

POLLUTION–Goal Is to Minimize or Eliminate Chemical

Gas Additive MTBE Haunts the Air and Water

Recent news stories have warned of its peril: MTBE, or methyl tertiary butyl ether.

This chemical, identified by the U.S. Environmental Protection Agency as possibly causing cancer, is showing up in our air and drinking water. Where does it come from, and how do you know if you are at risk for exposure?

MTBE has been used since the late 1970s as a gasoline additive, replacing lead to increase octane ratings. In the 1990s, it was also found to significantly reduce ozone and carbon monoxide levels. At that time, the EPA stepped up the use of MTBE as an oxygenate to concentrations as high as 15 percent by volume in some areas of the country as part of the 1990 Clean Air Act amendment mandates.

At first, these oxygenates were required only in areas with heavy air pollution. Now, much of the gasoline used in the country requires oxygenation, especially during the winter months. In the United States, a huge amount of MTBE, literally billions of pounds, is being produced each year at some 40 manufacturing facilities.

Unfortunately, the EPA failed to evaluate the possible environmental consequences, and MTBE was later identified as a potential human carcinogen. State and federal governments are now in the process of finding ways to minimize or eliminate the chemical from gasoline.

– Governor Orders MTBE

Be Removed From Gas

In California, Gov. Gray Davis issued an executive order March 25, 1999, that called for the “removal of MTBE from gasoline at the earliest possible date, but not later than Dec. 31, 2002.”

MTBE gets into our soil and groundwater mostly by way of petroleum products leaking from underground storage tanks and pipelines, and from surface spills. Additional sources include the atmosphere and urban runoff, as well as boats , particularly two-stroke engines , and other motorized water vehicles.

The federal government mandated that, by the end of 1998, all underground storage tanks must be upgraded to a double-walled containment system. The federal program gave owners and operators 10 years to bring their underground storage tanks up to standard by either upgrade or replacement, but not all have complied.

Even those who have upgraded or replaced their underground storage tanks have still been experiencing environmental contamination by MTBE, and experts have not yet been able to pinpoint how it is happening.

MTBE is quite volatile, compared to other compounds in gasoline. A possible explanation is that MTBE is being released as a vapor during gasoline storage and handling.

Because MTBE is also highly water-soluble, the vapor is easily dissolved in water. When released into the subsurface, MTBE is extremely mobile due to its low tendency to “sorb,” or “stick to,” soil, in comparison to other compounds in gasoline.

– Chemical Tends To

Stay In Groundwater

Highly soluble in water, the chemical spreads quickly through the groundwater and tends to stay there, as it does not readily biodegrade or volatilize.

Due to its mobility, high concentration levels, and persistence in the environment, technologies that have proven effective for gasoline releases without MTBE, such as bioremediation, are much less successful at cleanup of MTBE in groundwater.

Who should be concerned with testing for MTBE? Certainly owners and operators of fuel-containment facilities or nearby properties need to make the effort. If you are part of a water supply system that is groundwater-dependent, you too need to periodically run soil and groundwater tests.

Many cities across the nation, such as Santa Monica, have found such high concentrations of MTBE contamination in their groundwater that they have had to shut down some drinking water wells. Private single-family groundwater sources are at risk as well.

To test soil and groundwater for MTBE, the appropriate EPA-approved test methods should be used. However, if the methods are not carefully chosen, false results may be reported. For example, a laboratory may use EPA Method 8020 to test soil for gasoline-range petroleum hydrocarbons.

If gasoline is detected in a sample, any MTBE concentrations also reported are likely to be false positive results (incorrectly reported as real). A gas chromatography/mass spectrometry method like EPA Method 8260b is a better choice if you suspect MTBE.

– Traditional Strategies

May Work In Some Soils

For soil, traditional remediation strategies, such as soil vapor extraction and low-temperature thermal desorption, will continue to be effective at mass removal of contaminants such as MTBE in the right types of soil.

For groundwater, the EPA suggests that such traditional remedies as “pump-and-treat,” which involves pumping the water above-ground and treating it there, are likely to be of limited use and costly. Air sparging, which involves “injecting air directly into the groundwater to volatize the contaminants,” is much more promising.

An alternative commonly applied to gasoline releases, because it is far less expensive, is enhanced in situ bioremediation. Although it shows promise, in situ bioremediation is not yet a proven option for cleaning up MTBE.

Another viable option for many smaller groundwater sources is “point-of-use treatment.” Most carbon-based water filtering systems are capable of reducing MTBE to safe levels. While this procedure does not eliminate MTBE from groundwater, it does prevent it from coming out of our faucets and drinking fountains.

Who is paying for all of this cleanup? In California, the state’s Leaking Underground Storage Tank Cleanup Fund will pay up to $1.5 million to owners and operators of underground storage tank sites, on a corrective action claim per instance until the year 2011. If you are not a underground storage tank owner/operator, but your property is affected by adjacency, you may need to seek legal action to receive compensation.

If you think you may have an MTBE contamination problem with your groundwater, you should contact an environmental consulting firm to run tests on your soil and groundwater. Although the government is working to ban MTBE from gasoline, the procedure is a lengthy one, and the contaminant will continue to persist in our environment for some time to come.

Johnson founded Environmental Business Solutions, Inc., an environmental consulting firm.


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