The first meeting is set for 7 to 8:30 p.m. Tuesday at Ala Wai Elementary School's cafeteria.

The second will be held 7 to 8:30 p.m. Aug. 22 at Kapolei Hale.

The purpose of these meetings is to provide the public with an overview of O'ahu's wastewater treatment system and discuss the city's request that the U.S. Environmental Protection Agency continue to allow the Honouliuli and Sand Island wastewater treatment plants to operate with 301(h) waivers from full secondary treatment requirements.

For years the plants have been providing full primary treatment — and, in the case of Honouliuli, partial secondary treatment — to wastewater before discharging it more than a mile offshore, in ocean depths of about 200 feet, without any apparent detrimental effects to the marine environment or public health.

It will cost about $1.2 billion to upgrade these two plans to full secondary treatment, said Mayor Mufi Hannemann, in a news release. This cost doesn't include the increased cost to operate and maintain the expanded plants.

"These expenses are unnecessary at this time," Hannemann said. "Our first priority must be to work with EPA officials to address far more pressing needs to improve our collection system — the 1,400 miles of underground mains that carry wastewater to our treatment plants. It is the condition of our collection system that poses a risk to public health and that is where we must focus our efforts."

The EPA has extended the public comment period on the denial for Honouliuli's waiver to Aug. 27.

All concerned residents are encouraged to attend the meetings.