The City and County of Honolulu has reached a settlement agreement with the state Department of Health’s Clean Water Branch over the illegal discharge of bacteria-filled sewage into Kailua Bay in 2023.

DOH initially fined the city more than $434,000 for those effluent discharges exceeding permit limits for enterococci that occurred over 13 different days, from April to May 2023, from the city-owned Kailua Regional Wastewater Treatment Plant.

The settlement agreement addressed alleged violations of effluent limitations under the National Pollutant Discharge Elimination System Permit for the plant at 95 Kaneohe Bay Drive, the document states.

The state-imposed financial penalty, according to DOH, was due to the effluent discharges as well as the late submission of a required discharge monitoring report.

The city, per the agreement, will pay a penalty of $168,575.

“The settlement was for a reduced fine amount versus the DOH proposed fine,” ENV Director Roger Babcock told the Honolulu Star-Advertiser via email.

The settlement was signed by all parties and fully executed as of July 30.

On Oct. 9 the City Council voted unanimously to adopt the requested settlement between the city and DOH.

According to the final settlement agreement, on June 20, 2023, DOH issued a notice of violation and order, or NOVO, against the city asserting it violated state water pollution laws.

“While (the city) operated the facility, the respondent self-reported that it exceeded the permit’s maximum daily enterococci effluent limits thirteen times in April and May 2023 on: April 8, 19, 21-23, and 27-30, and May 1-4,” the agreement states. “While (it) operated the facility, (the city) self- reported that it exceeded the permit’s average monthly enterococci effluent limitation during the month of April 2023.”

The NOVO alleged the city’s self-reported exceedances resulted in 43 violations of state law, the agreement states.

Still, the approved agreement between DOH and the city Department of Environmental Services settles “their dispute without the risk of adverse findings of fact and conclusions of law, or a final order or judgment after litigation,” the document states.

According to Babcock, based on the same 2023 exceedances, the U.S. Environmental Protection Agency issued ENV an “administrative order on consent” outlining operational requirements and equipment improvements that need to occur at the wastewater plant in Kailua.

Those include:

>> Continuing the use of the Kaneohe-Kailua tunnel protocol — the $375 million gravity sewer tunnel project completed in 2018 that’s designed to increase storage capacity for Windward Oahu’s wastewater system and reduce the possibility of overflow — at the treatment plant.

>> Continue utilizing the supplemental operations and maintenance manual designed to optimize processes for meeting enterococcus permit limits.

>> Continue enterococcus monitoring a minimum of four times per week.

>> Install a continuous turbidity meter for effluent monitoring; installed and operational as of Dec. 15 2023.

>> Install ultraviolet disinfection system by Dec. 31, 2025.

According to Babcock, the Kailua treatment plant’s new UV system will cost $7.93 million.

“The notice to proceed was issued to the contractor March 26, 2024, and construction is currently underway,” he said. “With UV disinfection the plant will reliably remove 99.9% plus of enterococcus prior to discharge.”

He added the EPA also ordered the city to “keep both of the treatment plant’s biotowers in continuous operation until after the UV project is operational.”

Babcock noted the two biotowers will require refurbishment by Jan. 31, 2029 — work that’s expected to begin after the UV disinfection system is completed.

According to the EPA, enterococci are bacteria that live in the intestinal tracts of warmblooded animals, including humans.

Because enterococci are indicators of the presence of fecal material in water, they also could indicate the possible presence of disease-causing bacteria, viruses and protozoa, the EPA states.

These pathogens can sicken swimmers.

Other potential health effects can include diseases of the skin, eyes, ears and respiratory tract. Eating fish or shellfish harvested from waters with fecal contamination also can result in human illness, the EPA states.

According to DOH, the state will continue to monitor operations at the city-owned treatment plant in Kailua.

Meanwhile, Kailua Bay experienced more incidents of effluent exceedances earlier this year.

In May, city officials reported elevated levels of bacteria in effluent samples taken from the Kailua wastewater plant due to an extended period of torrential rainstorms.

That month, signs were posted warning ocean users to stay out of waters around the sewage outfall at Kailua Bay, which is about a mile from shore at a depth of 105 feet.

But similar incidents continued through the summer.

“ENV self-reported that the permit’s maximum daily effluent limits for enterococci were exceeded 11 times between May and July 2024, specifically May 7, 14, 17-19, 23, 31, June 20, and July 11, 14-15,” Babcock said.

As far as further DOH actions against his department, Babcock said that “there are no other pending cases between ENV and DOH.”