Thirteen days total.

That was the number of days that a city wastewater plant exceeded limits for enterococcus bacteria in its effluent in April and May, which prompted the state Department of Health to issue an advisory for all of Kailua Bay.

This, according to DOH, was a highly unusual and concerning event affecting public health. Enterococcus is an indicator of fecal material in water and therefore, the possible presence of pathogens that can sicken swimmers.

“It is the city’s responsibility to comply with their permit, and it is very concerning when a discharger does not meet their legal responsibilities,” said Bobbie Teixeira, DOH environmental health specialist. “It just shouldn’t happen.”

She added that 13 days of this is “extremely worrisome.”

“It’s very concerning to us, not only with the duration, but also the magnitude,” she said. “On some days they were exceeding by four, five, six times their permit limit, so it is unusual.”

While the turquoise-­colored bay at Kailua Beach Park — popular among visitors, local paddlers and kitesurfers — is now in the clear, and has been since May 5, health officials want to make sure the city remains in compliance.

Teixeira said the Health Department’s Clean Water Branch would work with the U.S. Environmental Protection Agency to investigate the incident and keep it from happening again, though she declined to go into detail on actions to be taken.

The city’s Kailua Regional Wastewater Treatment Plant is already under an EPA order issued in December to address similar pollution violations that occurred in early 2021.

The bacteria exceedances in 2021 occurred due to the failure of a biotower treatment unit at the plant, according to the EPA. But the plant’s discharge also exceeded bacteria limits in June 2020, April 2021 and December 2021.

Shoreline versus outfall

The most recent exceedances — which occurred between April 8 and May 4 — also resulted in mixed messaging to the public, according to Kailua beachgoers, who were confused by the advisories or missed them altogether.

While the city emphasized in its news releases and signs that high bacteria levels were possible near the deep ocean outfall — about 5,000 feet or a mile from the shoreline and 105 feet below the surface — the Health Department issued an advisory for all of Kailua Bay.

“We posted the advisory for the entire Kailua Bay, including the shoreline, because when there’s exceedances like this, we really don’t know where that plume of sewage is going to go,” said Myron Honda, supervisor of monitoring at the DOH Clean Water Branch. “That’s why out of an abundance of caution we had the city do the entire Kailua Bay shoreline.”

The city said during the exceedance period, it was testing both samples of treated effluent at the plant as well as samples from the Kailua Bay shoreline.

The city said daily shoreline samples since April 22 showed no exceedances except for four days, when runoff from heavy rain resulted in brown-water advisories. It also said monitoring at stations located around the outfall April 20, 24 and May 2 indicated the outfall had not affected the receiving water.

The results of enterococcus testing take 24 hours to process, but when there are exceedances the city must under its state permit notify DOH right away. DOH said it can post advisories on the same day it is notified.

The city, at DOH’s request, issued news releases and posted more than 20 signs warning the public along Kailua Beach — from as far north as Castles down to the main stretch and Kailua boat ramp.

Because it can be challenging to post signs at every access point, DOH encourages the public to subscribe to its online water quality advisory alerts, which are also posted online. Today, Honda said, there are just under 5,000 people who have subscribed to the alerts.

A brown-water advisory was simultaneously issued from April 28 to May 2, alerting the public of possible pathogens at Kailua due to a nearby stream flow.

Honda said brown-water advisories are based on a visual survey, without testing.

Samples over years have shown whenever there is heavy rain runoff, enterococcus levels almost always are exceeded, he said, and a brown-water advisory is issued. If there are three to four days of sunshine, then another visual survey will be conducted and the advisory lifted.

With only three staff members to conduct routine monitoring on Oahu, he said it would not logistically be possibly to test all brown waters on the island.

Double the trouble

What makes Kailua Bay even more vulnerable is that the ocean outfall there is shared by both the Kailua Regional Wastewater Treatment Plant and Marine Corps Base Hawaii’s Water Reclamation Facility.

And MCBH’s plant has also exceeded bacteria levels in its discharge, as recently as September 2021.

The EPA in August also ordered the U.S. Marine Corps to make improvements at the base due to exceedances of discharge limits.

Teixeira said the efflu­ent from both plants “co-mingles and goes out the same outfall, which is why we require testing of the effluent prior to the mixing and prior to it leaving their facilities so we can make sure whose effluent is meeting the limits or not.”

Roger Babcock, director of the city’s Department of Environmental Services, said in an earlier interview that the Kailua plant does not have a disinfection treatment process to kill bacteria such as enterococci, and is in the process of being upgraded.

While the Kailua plant has been the focus of the most recent violations, others on Oahu are also in dire need of improvements.

The EPA in 2010 issued a consent decree with the city ordering it to upgrade its entire wastewater collection sewer system to reduce sewage spills and comply with the Clean Water Act.

This includes major upgrades to the two largest plants — Sand Island and Honouliuli — which must be completed by 2035.