WASHINGTON – The impact of methyl tertiary butyl ether (MTBE) in groundwater in California may be more manageable than initially believed, researchers at the California environmental engineering firm Malcolm Pirnie and the Methanol Institute claim.
According to a new report prepared for the Methanol Institute by the environmental engineering firm, the assumptions initially used by researchers from the University of California in 1998 regarding the potential for widespread contamination of water supplies by MTBE are not supported by more recent data. The UC report was the basis for California Gov. Gray Davis' decision to ban the use of MTBE in 2003, due to concerns about what had been considered a threat to the state's environment. Methanol is among the primary components of MTBE.
According to the report, titled “Water Quality Impacts of MTBE: An Update Since the Release of the UC Report,” the key assumptions used by the UC researchers – that the frequency of MTBE detections found in public water supply systems during 1997 and 1998 could be extrapolated to 2012; that MTBE in groundwater would not biodegrade over time; that remediation technologies were unavailable to clean up existing MTBE plumes; and that MTBE contamination of surface waters would continue due to motorboat use – are no longer accurate, based on practical data collected since the initial UC study.
“A lot has happened since 1998 to dramatically reduce the threat of MTBE contamination of California's water supplies,'' said Methanol Institute President and CEO John Lynn. ``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.''
According to the new report, in 1998, the number of MTBE detections in drinking water sources was increasing fairly rapidly, suggesting that between 60 and 340 drinking water wells would become contaminated in the future, in addition to the 35 wells that had already been impacted. Since that time, 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 to 340 wells, the researchers claim.
The study also claims that, based solely on MTBE's physical and chemical properties, the UC researchers concluded that MTBE plumes would grow three- to four-fold and could extend up to 7,000 feet from a release site. Since 1998, MTBE has been shown to biodegrade under a range of environmental conditions, both in laboratory samples and in the field. These studies suggest that, depending on gasoline spill history, site geology and hydrogeology, MTBE plumes will often stabilize and with a few exceptions, do not span substantially longer distances compared to the plumes lengths of other gasoline constituents such as benzene, the new report claims.
The UC report concluded that where remediation was required, incremental costs for soil and groundwater treatment would be significantly higher for sites with MTBE due to the technical challenges of remediating MTBE impacted sites. But the new report claims current remediation and treatment technologies are effective at MTBE-impacted sites and are being widely applied on a national basis. Technologies including air sparging, pump-and-treat, multi-phase extraction and soil vapor extraction can be very effective at removing MTBE from soil and groundwater at a cost less than that projected in 1998. Emerging technologies such as in-situ bioremediation, which are now commercially available, may also decrease the costs of treating MTBE impacted sites.
The new study also points out that, since 1998, the continued phase-out of two-stroke engines on many of California's drinking water 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.
“Only a handful of the 11,000 unsampled public water supply wells in California are expected to test positive for MTBE, and likely at very low levels,'' Lynn said. ``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."
The Malcolm Pirnie report is available from the Methanol Institute's web site at http://www.methanol.org/reformgas/reports/WaterQuality.pdf .
