MARBLEHEAD – A gas line rupture prompted the Fire Department to bar access to Kimball Street at Ocean Avenue for just over an hour Thursday.Most residents were not home but landscapers were ordered away from the the intersection of the two streets after a contractor backfilling a hole broke open a high pressure natural gas line.”National Grid responded pretty quickly and we crimped the line. We laid (water) lines to hydrants and stood by,” said Fire Capt. Michael Porter.Porter said a private contractor hired by the town took precautions to dig around the gas line while making repairs to a water main. The gas line ruptured as the excavating equipment used by the contractor filled the hole with dirt.Engines 1 and 2 and Ladder 1 responded to the leak while Swampscott Engine 21 provided mutual aid, responding at one point to a report of outdoor natural gas at Fort Sewall. Fire officials opened Kimball and Ocean to public access at 12:53 p.m.