The County of Hawaiʻi Department of Environmental Management reported an unintentional bypass of the dechlorination system at the Pāpa‘ikou Wastewater Treatment Plant, resulting in the discharge of treated, disinfected wastewater with potentially elevated residual chlorine into the Pacific Ocean.

The failure began at an unknown time after staff left the facility at approximately 3 p.m. Oct. 20 and was discovered when employees returned at about 8 a.m. Oct. 21. Approximately 117,000 gallons of treated wastewater were discharged between 9 a.m. Oct. 20 and 8 a.m. Oct. 21, although the county said the volume discharged while the dechlorination system was inoperable could not be determined.

Staff added dechlorination tablets to reduce chlorine levels, which returned to normal at approximately 8:05 a.m. Oct. 21. The dispenser system was repaired and returned to operation at 12:56 p.m. The cause of the failure remains under investigation.

The county notified the Hawaiʻi Department of Health and is evaluating additional monitoring equipment and backup dechlorination methods to reduce the likelihood and potential impact of future failures.