Maryland officials are scrambling to find another strategy to finance the $425- million expansion of an aging Baltimore freight rail tunnel, following CSX Transportation’s withdrawal from the project earlier this month. Increasing the clearance inside the 120-year-old, 1.4-mile Howard Street Tunnel to accommodate double-stacked container loads was considered essential to expanding capacity at the Port of Baltimore. CSX, based in Jacksonville, Fla., had also agreed to a plan to split nearly two-thirds of the tunnel’s expansion cost with Maryland, with the remainder to be funded by a federal grant. In a statement, the railroad said the project “no longer justifies the level of investment.”