One of the Biggest Unknowns in the Unfolding Keystone XL Debate

One of the Biggest Unknowns in the Unfolding Keystone XL Debate

Michael S. Williamson/The Washington Post via Getty Images

The Valero refinery looms on the horizon in Port Arthur, Texas. It would be the end of the line for oil that would travel through the proposed Keystone XL Pipeline.