King County’s stellar credit ratings will help its wastewater utility save $160 million over the next 33 years — the largest savings in the county’s history for a bond refinance.

After Moody’s and Standard & Poor’s gave King County and its Wastewater Treatment Division Aa2 and AA+ ratings, respectively — citing the utility’s strong management practices, consistent financial performance and bright regional economic outlook — the county refinanced $728 million in outstanding bonds, which will save King County $15.9 million over the next three years.

“Our proven performance as financial stewards is paying record-setting dividends,” said Executive Dow Constantine. “The savings from this bond sale demonstrate how our commitment to creating the best-run government in the nation is delivering results for the people of King County.”