More than 5,000 pages of documents and photographs related to the Enbridge pipeline rupture have been released by the NTSB.  The National Transportation Safety Board is still investigating what caused the leak, which spilled more than 800,000 gallons of crude near Marshall in Calhoun County. Spokesman Peter Knudson said Monday the NTSB expects to reach a conclusion this summer.  The newly released material includes photos of the damaged pipe, reports outlining the sequence of events following the July 25, 2010 rupture and interviews with emergency responders and officials with Enbridge.  Enbridge announced plans last week to add a larger pipe to increase capacity, if they get government approval.