Nelson wants to fence off Mexico BY HENRY J. CORDES WORLD-HERALD STAFF WRITER There's a growing consensus in Washington that before Congress can address comprehensive immigration reform, it must first crack down at the nation's borders, U.S. Sen. Ben Nelson said Friday. Sen. Ben Nelson Nelson this week introduced a new border security bill, one that would go even further than the proposal he first outlined in September. Among the provisions added since September is the construction of a $5 billion, two-layer reinforced fence that would stretch from the Pacific Ocean to the Gulf of Mexico along the 1,900-mile U.S.-Mexico...