To meet regulatory requirements and improve Lower Kula water quality, the Piiholo Water Treatment Facility was built in 1996. The site access road improvements and water treatment plant required three years to build at a construction cost of $15.7 million. The facility is located in the Makawao Forest Reserve adjacent to the Piiholo Reservoir.
Piiholo uses direct filtration to treat its water, and chlorine as a disinfectant. In 2015, granular activated carbon and air-stripping were added to the treatment process in order to reduce disinfection-byproducts. This has significantly improved water quality and should ensure compliance with the state Department of Health as it relates to the removal of regulated contaminants for years to come.
Piiholo's average daily production is 3.24 million gallons per day.