California Monitoring Shows Drop In MTBE Groundwater Contamination
Chemical Policy Alert
October 11, 2002
© Inside Washington Publishers
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Demonstrating the success of aggressive new requirements on the controversial fuel additive methyl tertiary butyl ether (MTBE), new findings by California's Department of Health Services (DHS) show that of MTBE in groundwater are decreasing significantly. Officials credit a regional water board regulatory effort and a strong program regulating underground storage tanks (USTs) at service stations.
Out of 10,000 sources covering about 3,200 public water systems, 53 sources in the state recently reported having MTBE levels of more than 5 micrograms per liter (ug/L), which is the state's taste and odor standard, or secondary maximum contaminant level (MCL). MTBE's primary MCL, or the level at which a health impact is possible, is 13 ug/L. Detections greater than 13 ug/L have been reported in 23 sources, covering 11 counties. The findings </secure/data_extra/dir_03/epa2002_2933.pdf> update a list of MTBE detection levels taken over the last seven years.
"When you look at it as a whole, there's not that many sources directly impacted, at least in terms of public water system reports to us," says a DHS source. "That does not mean there is not a lot of MTBE sitting out there in shallow groundwater or contaminating . . . soils -- there still may be the potential for further contamination."
A 1998 UST-upgrade law and subsequent UST regulations have helped to significantly reduce the amount of MTBE detected in water wells and groundwater, according to officials. "I think, in part, aggressive programs by regional boards, the state Water Resources Control Board and the UST program made the difference," says a source. Cleanups of MTBE contamination also prevented spread to domestic wells, the source says. "I think the regulatory process is working."
If a water agency detects MTBE levels above the 5-ug/L threshold in its supply, it must inform the public of "what the cost is to mitigate the contamination, and then let the customers decide whether they want to assume that cost or accept the water the way it is," says a DHS source. If detections of 13 ug/L or higher are made, water agencies must close the wells and eliminate the MTBE contamination.