City officials today reported elevated levels of bacteria for the fourth day in effluent samples from the Kailua Regional Wastewater Treatment Plant due to the recent heavy rains.

Signs have been posted, warning the public to stay out of waters around the outfall at Kailua Bay, which is located about a mile from shore at a depth of 105 feet. The Hawaii Department of Health advises the public to stay out of Kailua Bay until further notice.

The Honolulu Department of Environmental Services said samples of treated effluent taken Friday, Saturday, and Sunday from the plant exceeded the daily maximum allowed under its state permit for enterococcus, an indicator of fecal material in water.

The recent bacteria exceedances are from samples taken at:

>> 10:13 a.m. on Friday

>> 8:28 a.m. Saturday

>> 9:39 a.m. Sunday

The first report of elevated bacteria Wednesday was from a sample taken Tuesday at 8:44 a.m., according to officials, which followed heavy rains on Monday.

The following Wednesday and Thursday, samples were in compliance before another onslaught of torrential rains fell on Oahu.

Due to the “sequential storm events” brought by the Kona low, city officials said the treatment plant experienced flows approximately five times greater than the average daily flow, which is believed to be the cause of the exceedances.

“Although the WWTP is still experiencing elevated flows due to inflow and infiltration from the ground being saturated with storm water,” officials said in a news release, “the treatment process efficiency is improving.”

The city said it will continue collecting daily samples of treated effluent from the plant until data confirms the enterococci levels are within permit limits.

It is also collecting daily samples at seven shoreline stations and says results continue to show “no shoreward movement” of effluent from the outfall.

Last year, the city was fined more than $434,000 for discharging effluent exceeding permit limits for enterococci from its wastewater treatment plant on 13 different days. The limits are set by a National Pollutant Discharge Elimination System permit issued by the state.

The city said after those exceedances that it plans to install an ultraviolet disinfection system at its plant, which should be operational on or before December 2025.

Last Monday, the state Health Department also issued a separate brown water advisory for Kailua Beach Park due to heavy rains, and stormwater entering coastal waters, which includes possible overflowing cesspools, animal fecal matter, pathogens and chemicals.

Following the “Kona low” storms, a brown water advisory was later issued for the entire island of Oahu. The islandwide brown advisory for Oahu still remains in place. When the water is brown, officials said, the public is advised to stay out.