The source of the oil is Northern Alberta.
There is not enough refinery capacity in Washington State to absorb the Athabascan oil. There is in Texas.
Moreover, most of the system has already been built. Phases 1 and 2 built from Manitoba to Steele City, NE then branches to the Wood River, IL refinery complex and the pipeline terminal at Cushing, OK. Phase 3 will be from Cushing to Texas. Phase 4 is the environmentally "sensitive" project -- a cut-off directly from Alberta to Steele City, NE.
This cut-off would not only increase capacity, it would also serve the Bakken field with a terminal in Baker, MT.
This project has been in the works for a long time. It's only at the last moment the enviros and the Obama administration have seen fit to blow the whistle.
Exactly, the pipeline isn’t ‘controversial’ because there’s some pristine ecological reason. It’s controversial for purely political/financial reasons. Cui bono?