NEW YORK--(BUSINESS WIRE)--On the effective date of April 22, 2015, Fitch Ratings will upgrade to 'AA+/F1+' from 'AA/F1' (Rating Outlook Stable), the ratings assigned to the District of Columbia Multimodal Revenue Bonds Medlantic/Helix Issue series 1998A tranche II (bonds). The rating action is in connection with the (i) substitution of the irrevocable direct-pay letter of credit (LOC) previously provided by JPMorgan Chase Bank, NA (rated 'A+/F1'; Stable Outlook) with a substitute LOC to be iss