The port of Miami's total debt is set to pass $1 billion after Miami-Dade County commissioners approved a $225 million bond offering on Tuesday to meet existing lending agreements and pay the balance on a nearly finished underground tunnel connecting the island-port to nearby highways. Auditors in March found a potential $1.6 million gap in the port's future payments toward its mounting debt stemming from an incentive to lure a new cruise ship into harbor last year, Deputy Mayor Ed Marquez told commissioners on Tuesday. He noted ratings agency Moody's said on Friday the seaport's rating would not be impacted due to healthy reserves and strong revenue. The port has $30 million in reserves, PortMiami Director Juan Kuryla told commissioners.