WASHINGTON - Shell Chemical L.P. and Shell Chemical Yabucoa have agreed to install pollution reduction equipment on two petroleum refining facilities at an estimated cost of $6 million as part of two comprehensive Clean Air Act settlements, the Justice Department and the Environmental Protection Agency today announced. The two companies will also pay a combined $3.3 million civil penalty to the United States as well as Alabama and Louisiana and $200,000 to Louisiana organizations for environmental education and emergency operations. Under the settlements, Shell Chemical L.P. will apply new air pollution control technologies and implement other measures to reduce emissions from some of the largest emitting units at its petroleum refining facilities in Saraland, Ala. and St. Rose, La.