Information on MTBEs From Santa Clara Water District
Additional information about MTBE, environmental impacts, and health effects can be found in the University Of California's Report, at: http://clu-in.org/download/contaminantfocus/mtbe/MTBEvol4.pdf
What is MTBE?
MTBE is a colorless chemical compound that is manufactured for use in gasoline. It is a common component in reformulated fuels developed to reduce smog and meet Clean Air Act goals. MTBE has been used in some gasoline as an octane booster since as early as 1979, but came into statewide, year-round use in 1996. In March 1999, GovernorDavis issued Executive Order D-5-99, which mandates the removal of MTBE from gasoline before December 31, 2002.
The characteristics of MTBE are unlike those of other gasoline constituents and solvents. MTBE is highly soluble and migrates quickly with groundwater. It does not significantly adhere onto particles, and it does not appear to readily biodegrade in the environment.
How does MTBE get into our waters?
MTBE can get into groundwater from leaking underground fuel storage tank systems and leaking petroleum pipelines. MTBE is thought to get into surface waters like lakes and reservoirs from the use of motorized watercraft. It may also travel into these waters in polluted runoff, or it may be deposited from the atmosphere by rainwater or other means.
How extensive is the occurrence of MTBE in Santa Clara County?
MTBE has been found at low concentrations in Coyote, Anderson and Calero reservoirs. It has also been found in groundwater at more than 300 leaking underground fuel storage tank sites currently under investigation by the district's Leaking Underground Storage Tank Oversight Program. The concentrations of MTBE at these sites has ranged from one part per billion to more than four million parts per billion. However, MTBE is mostly found in shallow groundwater, or groundwater that is that is very close to the ground surface. Most drinking water supply wells tap groundwater that is hundreds of feet below the surface. While very small amounts, ranging from 0.6 to 2.9 parts per billion of MTBE have been detected in at least one water supply well and some district treated drinking water, the concentrations are well below those believed by the U.S. Environmental Protection Agency to pose a health risk and below California's drinking water standards. The district is continuing to work with area water retail companies to test all the public drinking water supply wells in the county for MTBE and make sure customers receive water that is safe to drink and tastes and smells good.
Why is this issue a concern? Doesn't our drinking water get treated anyway?
In Santa Clara County, approximately half of our drinking water comes from groundwater supplies. The other half is from local and imported surface water supplies, and is treated by the District's three drinking water treatment plants. Research suggests that drinking water treatment technology in place now does not remove MTBE from drinking water. To implement a system that will remove MTBE from drinking water is likely to be extremely expensive. In Santa Monica, MTBE contamination led officials to shut down half of the city's drinking water supply wells, leading to greater dependence on more expensive imported water. It is the goal of the district and the water retail companies to ensure that this does not happen in Santa Clara County.
What are the health effects of consuming MTBE?
There is little data regarding the health effects of human exposure from drinking MTBE contaminated water. However, the Environmental Protection Agency has issued a drinking water advisory of 20 to 40 parts per billion MTBE that protects the consumer from unpleasant taste and odor and from potential health effects. The California Department of Health Services, Office of Drinking Water has adopted a 5 part per billion drinking water standard that protects consumers from unpleasant tastes and odors. In addition, the California Office of Environmental Health Hazard Assessment has adopted a public health goal of 13 parts per billion MTBE in drinking water to protect consumers against health risks over a lifetime of exposure.
Will boating on water supply reservoirs be banned?
The water district Board of Directors considered banning gasoline-powered watercraft from Anderson, Coyote and Calero reservoirs during the 1998 boating season to control levels of MTBE concentrations. However, the board in concert with the Santa Clara County Parks and Recreation Department adopted a compromise program for the 1998 boating season. The program was revised in April 1999, with the goal of keeping MTBE concentrations in the reservoirs below 3 ppb.
My drinking water comes from a private well. How can I tell if it has MTBE in it?
MTBE has a distinctive, solvent-like odor that is detectable at relatively low concentrations which have been reported to range from 10 to 130 parts per billion. The actual range of detection may vary widely depending on an individual's sense of smell and on the type and temperature of the source water. The only definitive way to determine if there is MTBE in water is to have it chemically analyzed. The district is investigating areas of known MTBE contamination which may pose a threat to private water supply wells and, at the owner's request, sampling specific private wells that might be at risk.