A special exemption from 2017 allowed the Keystone Pipeline to operate at pressures above the standard for crude oil transport, a report from the federal government shows. The exemption is receiving new scrutiny following last week’s oil spill in northern Kansas, the largest in the pipeline’s history. The cause of last week’s record breaking oil spill is still unknown, but some activists and a state lawmaker are highlighting a need to learn more about this exception to run the pipeline at higher pressure. “We know that the pipeline has been plagued by inherent problems associated with its orig...