Highline Water District's bond rating recently was revised by Standard & Poor's to AAA, the highest possible rating.

Previously, Highline, which serves approximately 18,000 residential and commercial customers in Southwest King County, had a rating of AA-.

Highline, which was formed in 1946, serves parts of Burien, Normandy Park, Des Moines, Federal Way, Kent, SeaTac, Tukwila and unincorporated King County.

It was one of four water, sewer and/or drainage utilities in Washington - and only 16 nationally - to be upgraded to an AAA rating from Standard & Poor's Rating Services, which raised the bond ratings of 130 such utilities.

"This shows that our district is doing something right financially to be rated at the AAA level," said General Manager Matt Everett. "This is even higher than Seattle Public Utilities, which was recently upgraded to a AA+ rating."

Standard & Poor's noted that the district's only debt - bonds for Crestview Reservoir in Tukwila - mature this year, and "there exists ample capacity for additional bonds that it may issue."

The AAA rating is based on the district's "service coverage and cash reserves; good economic fundamentals" including "housing market vulnerabilities, employment softness, or cost of service inflation; and solid management, which includes a demonstrated willingness to adjust rates, long-term planning to fund key service components like water supply ... and the ability to serve the needs of a growing community."

Everett said the district may issue more than $4 million in bonds later this year for construction of the McMicken Heights Water Treatment Plant, depending on what Congress does with an economic stimulus package that would include funding for infrastructure projects.

The treatment plant is on the list of projects under consideration for funding if the stimulus package is approved. "If not," Everett added, "we will sell bonds and get more favorable interest rates because of our new higher bond rating, which will save ratepayers money."

Additional savings will be realized because the district won't have to pay for insurance to guarantee the bonds with its AAA rating," he noted.