NEW YORK (Standard&Poor's CreditWire) Sept. 10, 1999-- Standard&Poor's today lowered its rating on the District of Columbia's $44.5 million general fund recovery bonds series 1991B-2 to double-'A'-minus/'A-1'-plus from double-'A'/'A-1'-plus. Standard&Poor's also affirmed its double-'A'-minus/'A-1'-plus ratings on the District of Columbia's $50.3 million general fund recovery bonds series 1991B-1 and $41.4 million general fund recovery bonds series 1992B-3. The rating downgrade on the series 1991B-2 bonds reflects the substitution of the letter of credit (LOC) provided by National Westminster Bank PLC with a LOC provided by Bank of America. The ratings on the series 1991B-1 and 1991B-3 bonds are affirmed following Standard&Poor's review of the LOCs provided by Société Genérale and Bank of