The Sand Island plant's discharged water currently does not meet water quality standards set to protect marine life or human consumption of fish.

"Today we have made a tentative determination that the Sand Island plant does not meet the Clean Water Act requirements, and will need to be upgraded to provide improved wastewater treatment prior to discharging into Hawaii's ocean waters," said Wayne Nastri, the EPA's Administrator for the Pacific Southwest region.

"Through this action and findings we made earlier this year regarding the Honouliuli plant, we intend to work with the city to upgrade its two largest wastewater plants. These upgrades will ensure that Hawaii's residents, visitors and marine life benefit from the full protections provided by the Clean Water Act."

The city's Sand Island plant, located in Honolulu, is currently operating under a variance from secondary treatment. If the EPA's proposal becomes final, the plant will be required to upgrade to full secondary treatment.

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 different biological treatment techniques that allow the bacteria to consume most of the waste's organic matter.

The EPA's tentative decision will be available for public comment through Feb. 29, 2008. A public hearing on the tentative decision will be held on Feb. 5, 2008 at 6:30 p.m. at the Washington Intermediate School. At the completion of the public comment period, the EPA will consider all public comments and make a final decision on the variance application.

The federal Clean Water Act generally requires municipal wastewater treatment plants to use both primary and secondary treatment. Amendments to the act in 1977 allow for variances from secondary treatment for marine discharges, provided the plant meets water quality standards and other specific criteria as part of section 301(h) of the act. These variances are sometimes referred to as 301(h) waivers. Many coastal cities that once sought variances from secondary treatment, especially in areas where there is heavy recreational beach use, have chosen to upgrade their treatment plants to meet Clean Water Act requirements without variances.