Wai'anae Wastewater Treatment Plant

  • Drinking water is sourced from the aquifers in areas of the Koʻolau & Waiʻanae Mountain ranges and pumped to your home via water mains.

  • Untreated wastewater is conveyed through sewer mains along the coastline from the Waiʻanae Coast which includes Nanakuli, Lualualei, Maili, Waianae, and Makaha. The wastewater then arrives at the Waiʻanae Wastewater Treatment Plant where it undergoes secondary treatment.

  • The entirety of the wastewater received at Waiʻanae WWTP is disposed of through a deep ocean outfall at 107.5 feet below the surface and 6,184 feet offshore.

  • Treated wastewater flows through an outfall pipe and is discharged into receiving waters (the ocean). The introduced wastewater can then mix with ocean water, be carried by currents to nearby coral reefs and possibly affect the health of these ecosystems.

  • Oʻahu's Drinking Water Sources

    Oʻahu relies solely on underground water sources for drinking water which are all dependent on three natural elements: northeast trades, high mountain ranges, and the island's geological landscape. The NE tradewinds drive clouds filled with moisture inland, the high mountain ranges (Koʻolau mountains and Waianae mountains) capture and force moisture-filled clouds to higher elevations which causes rainfall on watershed areas. The Hawaiian Island geological landscape serves as a natural filter and underground storage system of water. Rainwater percolates into the earth, filtered by volcanic rock, and stored in aquifers. The aquifers are an underground freshwater reservoir storage from which the Board of Water Supply sources water to deliver to homes. Water is pumped from a network of shafts, water tunnels, and many wells located all over Oʻahu, (except for the North Shore area) and conveyed to homes through mains, booster systems and reservoirs.

    Oahu's Drinking Water Sources
  • Wai'anae Wastewater Treatment Plant Facility
    Wai'anae Wastewater Treatment Plant
  • Deep Ocean Outfall Map
    Waianae Deep Ocean Outfall Map

Do You Know What Happens After You Flush?