The rating on Philadelphia, Pa.'s water and wastewater revenue bonds series 1997B has been affirmed due to the bank facility being extended to Oct. 24, 2013. The long-term component of the rating is based on Ambac Assurance Corp. The short-term component of the rating is based on KBC Bank N.V. The stable outlook is based on the outlook of the bond insurer, Ambac Assurance Corp.