The U.S. Environmental Protection Agency (EPA) and the Department of Justice recently announced a settlement with HollyFrontier Corporation subsidiaries (HollyFrontier Refining & Marketing LLC, Frontier El Dorado Refining, LLC, Holly Refining & Marketing Company-Woods Cross, LLC, and Navajo Refining Company, LLC) that resolves alleged Clean Air Act violations regarding fuel quality emissions standards and testing requirements at three HollyFrontier facilities.