In this Tuesday, June 28, 2011, file photo, an oil tanker is docked at the Exxon Mobile Baytown complex along the Houston Ship Channel in Baytown, Texas.  Exxon is considering a multi-billion-dollar expansion of  the giant petrochemical complex east of Houston. The energy company has filed applications with the U.S. Environmental Protection Agency and the Texas Commission on Environmental Quality for permits to build an ethane cracker at the Baytown complex and two high performance polyethylene lines at its nearby plastics plant in Mont Belvieu. (AP Photo/David J. Phillip, File)
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