On December 20, 2010, Moody's Investor Service lowered its rating on $4.6 billion of water and sewer bonds issued by the Detroit Water and Sewerage Department.
Moody's lowered to A1 from Aa3 the credit rating on $1.43 billion of outstanding sewer bonds secured by a senior lien pledge of net revenue, and lowered to A2 from A1 on $1 billion of revenue debt secured by a second lien. At the same time, Moody’s lowered to A1 from Aa3 the rating on $1.54 billion of senior lien water bonds and to A2 from A1 on $660 million of second lien water bonds.
All of Detroit's water and sewer revenue bonds are now graded in the "Upper Medium Grade" category, down from "High Grade." Moody's also revised its outlook for Detroit's water and sewer bonds to negative.
Moody's cited the risk from interest-rate swaps and "lean financial flexibility" that could crimp Detroit's ability to service this debt. Moody’s said debt service coverage on the bonds has diminished amid the economic slump that has hit the Detroit area and because of large payments it may face to cancel interest- rate swaps.