(Portland, OR)  --  Portland is among a number of cities across the U.S. where protests are taking place against the multi-billion-dollar Dakota Access pipeline.  The U.S. Army Corps of Engineers has stopped the controversial project to allow more study and additional input from the Standing Rock Sioux tribe, which says the pipeline threatens property on its reservation.  Hundreds of demonstrators staged their second pipeline protest yesterday in front of the Army Corps of Engineers office in Northeast Portland.  KOIN-TV reports the protest caused delays to all TriMet service in downtown Portland.