MTBE (Methyl tertiary - butyl ether)

Methyl tertiary - butyl ether (MTBE) is a chemical that is often added to gasoline to reduce air pollution.
Image of MTBE 3D drawingIn the 1990's, MTBE was added to gasoline sold in California to make gasoline burn more completely and reduce harmful air emissions. MTBE was credited with contributing to major air quality improvements in the state, reducing emissions by 3 million pounds every day which is equivalent to taking 3.5 million cars off the road. While MTBE may have been good for air quality, when released from underground storage tanks (USTs) it negatively impacted ground water. Due to its small molecular size and solubility in water, MTBE moves rapidly through water, much faster than other gasoline constituents. When MTBE gets into a drinking water supply, it imparts a foul odor to the water and above certain concentrations may pose health concerns. During the summer of 1997, the US Geological Survey found detectable levels of MTBE in Lake Tahoe to a depth of 90 ft. To protect Lake Tahoe and its residents, fuel containing MTBE was banned from sale in the Lake Tahoe Basin within El Dorado County.

MTBE Ordinance No. 4553(PDF, 9KB), March 28, 2000 (South Lake Tahoe ban on MTBE fuel)

In 2004, fuel containing MTBE was banned from sale in the State of California. Today air quality improvements once provided by MTBE are derived from the addition of ethanol to gasoline.   

Prevention of Fuel Releases from Underground Storage Tanks

El Dorado County Environmental Management Department (EMD) is mandated to enforce the California Underground Storage Tank Law and Regulations which require all fuel stations to perform on-going underground tank and piping testing. More importantly, by December 22, 1998 (the state and federal deadline), all fuel stations were required to upgrade their underground storage systems with corrosion resistant double wall tanks and piping, overfill protection and leak detection devices. This design is very simple--if the inner tank or pipe develops a leak, the outer shell will contain the fuel and the leak detection system will notify the operator of a problem. The Department performs inspections of each UST system every year.

Owners and operators of UST systems are required to by law to report any unauthorized releases and failures in their monitoring systems to EMD. EMD staff then work with operators to ensure repairs are made and releases are remediated. Operators must order the correct amount of fuel to be delivered and monitor fuel delivery to their tanks. They are required to have spill plans and cleanup materials on site to contain any spills.

Even the smallest spill of gasoline has the potential to contaminate thousands of gallons of water. Consumers must not overfill tanks when fueling vehicles, boats, snow blowers, lawn mowers and other gas-powered equipment. Never use gasoline to kill weeds. Old gasoline can be taken one of the household hazardous waste facilities located in South Lake Tahoe, Diamond Springs and El Dorado Hills. 

If you have any questions, please contact Environmental Management Department in South Lake Tahoe (530) 573-3450 or in Placerville (530) 621-5300.