A caravan that environmentalist and renowned climate-change writer Bill Mckibben calls the “largest collective act of civil disobedience in the history of the climate movement” will roll through Boulder and Denver next week to protest the proposed Keystone XL Pipeline from Alberta, Canada, to the Gulf Coast of Texas. Designed to carry oil from the tar sands production fields of Canada to oil refineries on the Gulf Coast, the nearest the pipeline comes to Colorado is Nebraska, but activists point out that tar sands oil already comes into Commerce City by pipeline and is then refined by Suncor Energy and sold as gasoline across Colorado at nearly 270 Shell and Phillips 66 stations.