So far, political concerns of individual posters have outweighed most of the facts in this thread. Here are a few points to clarify.
First, Canadians would like to have refineries built in Canada, rather than ship jobs south with the oil, but Big Oil (Exxon, Shell, BP, etc) control the oil industry here (as they do in the US), as well as much of the government policy, and they don't want a surplus of refining capacity driving down the price of gas.
Second, TransCanada already has a longer pipeline right-of-way skirting the Ogalala aquifer, and the pipeline would have been building long ago if they had chosen to follow that route. The short-cut they proposed across sensitive environmental areas, for economic reasons, is what has caused most of this dispute, along with some very poor pipeline maintenance which has resulted in some disastrous recent spills.
Third, everybody should read this or something similar.
http://www.waterencyclopedia.com/Oc-Po/Ogallala-Aquifer.html