In 2019, EPA began investigating the causes of high fenceline concentrations of benzene at the Sinclair Navajo petroleum refinery in Artesia, New Mexico. The reports submitted by Navajo showed that the Artesia Refinery had a very high average annual fenceline benzene concentration. EPAs investigation led to Navajos removal of the main source of the high benzene levels, but also revealed that Navajo had failed to undertake appropriate corrective actions, as required by CAA regulations for the control of hazardous air pollutants at petroleum refineries, per 40 CFR Part 63, Subpart CC. EPA has also determined that Navajo has violated new source performance standards located at 40 CFR Part 60, Subparts A, Ja, and QQQ, and additional provisions of 40 CFR Part 63, Subpart CC related to flares and emission controls for storage vessels.