The U.S. Environmental Protection Agency decided today to not renew the City and County of Honolulu's waivers exempting the Sand Island and Honouliuli Wastewater Treatment plants from full secondary treatment requirements.

If upheld, the decision could force the city to upgrade both plants to bring them within compliance of federal laws, and city officials have said the upgrades could cost more than $1.2 billion.

Honolulu Mayor Mufi Hannemann issued a statement this afternoon expressing disappointment but not surprise, at the EPA decision because the decision followed tentative denials of the variances in 2007.

"Every indication was that the EPA would decline to renew the waivers these plants have operated under for so long, so today's decision was not unexpected," said Hannemann, in a statement. "However, we had hoped that the EPA would reconsider its tentative decision, in light of the overwhelming evidence presented by our local scientists and engineers that secondary treatment at these plants is not necessary or beneficial. We will review the final decision, and in all likelihood seek a review, as provided for by the EPA regulations."

The EPA has concluded that the discharges from the two plants do not meet the Clean Water Act's conditions for renewed variances from requirements that apply to most of the nation's municipal sewage treatment plants, according to a news release. Specifically, the discharges from the two plants do not meet all applicable water quality standards and neither of the plants' discharges protect recreational use or marine life in the vicinity of the ocean outfalls, according to the news release.

Based on those criteria, the two plants do not qualify for renewed variances.

"This action will ensure that residents and visitors using Hawai'i's ocean waters are protected from inadequately treated sewage," said Wayne Nastri, the EPA's Administrator for the Pacific Southwest region, in a statement. "We will work with the city on a realistic schedule to upgrade its two largest wastewater plants, taking into account the other priorities for improvements to Honolulu's wastewater system."

The city's Sand Island plant, located in Honolulu, and the Honouliuli plant, located in 'Ewa, were both operating under variances from secondary treatment, for nearly two decades.

In reaching these final decisions, EPA considered nearly 600 comments received in writing and presented verbally at two public hearings, according to the news release. Written responses to all comments received have been posted on EPA's Web site. In response to these comments, EPA made modifications to tentative Decision Documents released in 2007, but these changes did not alter the overall conclusions that the two plants do not qualify for renewed variances.

Primary treatment generally involves screening out large floating objects, such as rags and sticks, removing grit, such as cinders, sand and small stones, and allowing wastewater to settle, followed by the removal of collected solids. When secondary treatment is used, primary-treated wastewater flows into another facility where a large portion of the organic matter in the wastewater is removed by making use of the bacteria in the sewage. There are a variety of biological treatment techniques that allow the bacteria to consume most of the waste's organic matter.