Rotting holes in steel support beams, enormous rust patches, small splits in steel girders and broken bracing are evident all along the underside of the John Greenleaf Whittier Bridge, the heavily traveled Interstate 95 span that crosses the Merrimack River between Amesbury and Newburyport. A just-released state safety report filed in the wake of last year's disastrous collapse of the similarly designed Interstate 35 bridge in Minneapolis gave the 57-year-old Whittier Bridge "poor" ratings due to deterioration. On a 10-step ranking system, the rating is just two steps above the point where engineers consider closing a bridge due to safety...