For the past decade, the U.S. shale boom has mostly passed by California, forcing oil refiners in the state to import expensive crude. Now that’s changing as energy companies overcome opposition to forge ahead with rail depots that will get oil from North Dakota’s Bakken Shale. Thanks in large measure to hydraulic fracturing, the U.S. has reduced oil imports from countries such as Iraq and Russia by 30% over the last decade. Yet in California, the use of imports has shot up by a third to account for more than half the state’s oil supply.