SEATTLE, March 2 - The drugs move across the Canadian border inside huge tractor-trailer rigs, pounds and pounds stashed in drums of frozen raspberries, tucked in shipments of crushed glass, wood chips and sawdust, or crammed into hollowed-out logs, in secret compartments that agents refer to as "coffins." Kayakers paddle them south from British Columbia across the freezing bays of America's northwest corner, and well-paid couriers carry up to 100 pounds at a time in makeshift backpacks, hiking eight hours over the rugged mountainous terrain that forms part of the border between the United States and Canada. Small planes drop...