The U.S. Environmental Protection Agency (EPA) reports that as of September 2020, there have been 559,000 releases from underground storage tank (UST) sites. Although many of these sites have been remediated and closed, there are still 62,000 open sites that require attention. These sites are either undergoing remediation or have been identified as needing remediation for one or more contaminants of concern (COCs).
The primary COCs that require remediation at petroleum sites include benzene, toluene, ethylbenzene, xylenes, polycyclic aromatic compounds (PAHs), methyl-tertiary butyl ether (MTBE), and total petroleum hydrocarbons (TPH). Benzene and MTBE are particularly important due to their low cleanup levels, based on EPA's Maximum Contaminant Levels (MCLs) in drinking water. The MCLs for benzene and MTBE are 5 and 20 micrograms per liter (ug/L), respectively.