Study disputes assumptions for California's ban on MTBE in gasoline

Oct. 4, 2001
The Methanol Institute says the potential for groundwater contamination by the gasoline additive methyl tertiary butyl ether has been overstated.

By the OGJ Online Staff

WASHINGTON, DC, Oct. 4 -- A report prepared for the Methanol Institute concludes that the potential for widespread contamination of groundwater by the gasoline additive methyl tertiary butyl ether has been overstated.

The Malcolm Pirnie environmental engineering firm evaluated assumptions used by University of California researchers in 1998. The UC report was the basis for Gov. Gray Davis' decision to ban the use of MTBE in 2003 due to concerns about its threat to drinking water supplies.

The UC report assumed the frequency of MTBE detections found in public water supply systems in 1997-98 could be extrapolated to 2012; MTBE in groundwater would not biodegrade over time; remediation technologies were unavailable to clean up existing MTBE plumes; and MTBE contamination of surface waters would continue due to motorboat use.

John Lynn, Methanol Institute president, said, "A lot has happened since 1998 to dramatically reduce the threat of MTBE contamination of California's water supplies. The state intended to act prudently in 1998. Now that we know the water quality impacts of MTBE are manageable, it would be imprudent to ask Californians to pay an extra $1 billion at the pump to switch to ethanol."

The Malcolm Pirnie report said since 1998, as more wells have been tested, the percentage of newly contaminated wells has decreased. Based on current detection rates in newly sampled wells, only 16 new wells are projected to be impacted, compared to the UC estimate of 60-340 wells.

It said since 1998, MTBE has been shown to biodegrade under a range of environmental conditions and MTBE plumes do not span substantially longer distances compared to the plumes lengths of other gasoline constituents such as benzene.

It said current remediation and treatment technologies have been effective at MTBE-impacted sites, at a cost less than that projected in 1998.

And Malcolm Pirnie said the continued phaseout of two-stroke engines on many California reservoirs has greatly reduced the risk of MTBE contamination. In addition, studies have shown that MTBE will not persist in surface waters, but will volatilize within a relatively short time.

Lynn said rather than ban MTBE use, "The key is to identify gasoline leaks from underground storage tanks early and remediate impacted sites immediately, before groundwater resources may become contaminated. That's exactly what is being done in California today."