What is MtBE and why has it been a focus of concern?
MtBE is methyl-tertiary-butyl ether. It is a highly volatile liquid chemical which is added as an oxygenate to reformulated gasoline at a concentration of roughly 2-12%. MtBE has been used in gasoline in the United States since the late 1970’s when lead was phased out as an anti-knock agent. It has a relatively high solubility of 4.8 grams per 100 grams of water at room temperature and is also known to have a disagreeable taste and odor even at low concentrations. Gasoline which contains MtBE and other petroleum products can impact groundwater as a result of leaking USTs or spills. Since MtBE is more soluble in water than most other constituents in gasoline it can move more quickly in the environment and at times extend well downgradient of the other constituents. For this reason, it has been found as a contaminant in drinking water supply wells throughout the state. The State DHS drinking water standard (MCL) for MTBE is 0.013 milligram per liter (mg/L), or 13 micrograms per liter (µg
