Heavy rains trigger 140,000-gallon wastewater spill at Waimea plant

Residents are being told to stay out of Kīkīaola Small Boat Harbor waters after heavy rains overwhelmed the Waimea Wastewater Treatment Plant and sent an estimated 140,000 gallons toward the west-side harbor. Warning signs were posted where the spill could enter the water, and county officials said no one should make contact until the Hawaiʻi State Department of Health gives clearance.

The overflow ran from about 7:50 a.m. to 4:20 p.m. on April 10, according to the county’s update. An earlier county notice had estimated about 72,000 gallons had spilled by the time of that first release. The county said the release came from an effluent tank after wastewater had already gone through biological treatment and ultraviolet disinfection, but storm-driven high flows and infiltration and inflow overwhelmed the system. That distinction matters, but the public-health warning does not change: avoid the harbor water, and keep children, swimmers, surfers and boaters out of the affected area until state testing clears it.

Anyone who may have come into contact with the water can check the Department of Health’s Clean Water Branch system, which posts water-quality advisories, sewage-spill notices and beach notifications. The county said questions can be directed to Donald Fujimoto of the Wastewater Management Division at 808-241-4083 or dfujimoto@kauai.gov. The spill landed during the same storm system that was already driving brown-water conditions and water-quality advisories in parts of Kauaʻi, raising the risk for anyone using west-side coastal waters for fishing, paddling or recreation.

The county also said crews were working to repair infiltration-and-inflow pathways and to coordinate with the health department on possible system changes, including expanding underground injection control wells and R-1 reuse distribution to better handle heavy storm flows. The Waimea plant has been described as a 300,000-gallon-a-day facility with a planned expansion toward 700,000 gallons a day, a reminder of how quickly West Kauaʻi infrastructure can be strained when rain saturates the ground and runoff surges into the system.

Kīkīaola Harbor sits in a drainage corridor that has already faced Clean Water Act litigation and settlement work over plantation-era ditches on the Mānā Plain. That history is why this spill will draw close scrutiny, not only for the water people use this weekend but for whether Kauaʻi County can prevent the next storm from turning a treatment plant problem into a harbor closure.