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Wastewater Treatment Plant:  Kailua Regional WWTP

Kailua Regional Wastewater Treatment Plant (1965)
  • Secondary level of treatment
  • Processed 10.37 million gallons per day (FY13)
  • Deep ocean outfall (5,083 ft. offshore/110 ft. deep)
  • Estimated 20-year CIP funding: $464 million

The Kailua Wastewater Treatment Plant was originally built in 1965 to serve Kailua town and surrounding communities. 


Regional treatment was implemented in 1994, when the former treatment plants at Ahuimanu and Kaneohe were converted to preliminary treatment facilities, and the Kailua WWTP was expanded to accommodate the flows from these areas. The Kailua Regional WWTP now serves the Koolaupoko District on the Windward side of Oahu from Kahaluu to Keolu Hills, encompassing Ahuimanu, Kaneohe, Kailua, Aikahi Park, Maunawili, Kailua Heights, Enchanted Lake and Lanikai.  This was done to eliminate discharge of treated wastewater into Kaneohe Bay.


Wastewater is conveyed to the Kailua Regional WWTP via 26 pump stations and two preliminary treatment facilities, where it receives a secondary level of treatment.  The treated effluent is discharged through the 48-inch Mokapu Outfall (not within Kailua Bay), which extends 5,083 feet offshore (the last 983 feet through diffusers) at an average depth of 110 feet.


The KRWWTP operates under a National Pollutant Discharge Elimination System (NPDES) Permit effective as of Sept. 3, 2006, and expired on June 30, 2009.  The plant reapplied for the permit, but is discharging under an administrative extension until the state Department of Health reviews the application and issues a new permit.  The NPDES permit and applicable Zone of Mixing (ZOM) authorizes the City and County of Honolulu to discharge secondary treated wastewater from facility to receiving waters (Pacific Ocean) east of the Mokapu Peninsula through its deep ocean outfall in accordance with the effluent limitations, monitoring requirements and other permit conditions.

Last Reviewed: Wednesday, July 24, 2013