Ground zero for Hawaiʻi’s cesspools.

Where it hurts most

Five places the State has flagged.

In 2017 the Hawaiʻi Department of Health named five Hawaiʻi Island areas where cesspools pose the greatest risk to drinking water or sensitive coastal waters.

1. 01 · South Kohala

   Puakō

   The problem. Puakō is a small coastal community — a main road with homes on either side, some just feet from the ocean — that relies entirely on on-site wastewater systems. With little soil and groundwater close to the surface, UH Hilo dye-tracer studies found wastewater from homes emerging from shoreline springs within six hours, and a NOAA study measured it moving 13 to 250 feet a day.

   The impact. Bacteria exceeded State recreational standards in the water fronting 81 percent of homes sampled, and the Division of Aquatic Resources found coral cover down 35 percent with algae overgrowth up 38 percent over 30 years. Bacteria were elevated whether a home used a cesspool, septic tank, or aerobic unit — so researchers recommended a community wastewater treatment plant, and the Legislature funded its planning in 2019. In places like Puakō, the right fix may be shared infrastructure rather than house-by-house systems.

   Sources: University of Hawaiʻi — Puakō sewage runoff study (2021) · Journal of Hydrology: Regional Studies — Puakō study · DOH 2017 cesspool priority report (poster)

2. 02 · Puna District

   Keaʻau & Puna

   The problem. About 17 percent of all the cesspools in Hawaiʻi — roughly 9,300 — are packed into a corridor about 4.3 miles wide on Kīlauea’s east slope, along the path groundwater flows. There’s little to no soil to slow them down: University of Hawaiʻi research found wastewater can reach the water table in a fraction of an hour. Much of the area has no public water system, so many households rely on private wells or rain catchment.

   The impact. The Department of Health found wastewater indicator bacteria in a quarter of the domestic wells it sampled here — a direct threat to drinking water. It was the island’s highest-ranked area in DOH’s 2017 report.

   Sources: DOH 2017 cesspool priority report (poster)

3. 03 · Hilo

   Hilo Bay

   The problem. Nearly 9,000 cesspools discharge to the streams and groundwater that flow into Hilo Bay. On the island’s wet windward side, large volumes of water reach the bay — and its breakwater, which shelters it from the open ocean, also slows how quickly that water is flushed out.

   The impact. University of Hawaiʻi at Hilo research has found elevated nutrients and fecal indicator bacteria in the bay and the rivers feeding it, with the highest bacteria levels during brown-water events. The Department of Health regularly issues brown-water advisories warning people to stay out of the water.

   Sources: UH Hilo — brown water advisory research · DOH 2017 cesspool priority report (poster)

4. 04 · North Kona

   Coastal Kailua-Kona

   The problem. About 6,500 cesspools sit along the Kona coast, where groundwater flows straight to West Hawaiʻi’s economically vital reefs. State groundwater modeling indicates nitrate from on-site wastewater systems may exceed 10 mg/L in the aquifer — a heavy nutrient load for coral.

   The impact. A survey of West Hawaiʻi reefs found steep coral declines at multiple sites, many of them matching areas with dense on-site wastewater systems or wastewater injection. UH Hilo researchers also traced cesspool sewage from homes near Aliʻi Drive into Kahaluʻu Bay within about one tide cycle; the beach often exceeds state bacteria standards and has drawn DOH advisories.

   Sources: UH Hilo — sewage leaking into Kahaluʻu Beach Park (2024) · Surfrider Foundation — Blue Water Task Force 2023 · DOH 2017 cesspool priority report (poster)

5. 05 · Lower Puna

   Kapoho

   The problem. Kapoho is fronted by the tide pools of the Waiʻōpae Marine Life Conservation District, which have only a limited connection to the open ocean. That shelter means slow water turnover, leaving the pools’ abundant coral vulnerable to pollution from land. UH Hilo research estimated sewage made up about 27 percent of the nutrient load to the tide pools, weakening the coral’s ability to resist algae.

   The impact. Much of the community — and the tide pools — was covered by the 2018 Kīlauea lava flow. Any rebuilding on remaining lots has to meet today’s wastewater rules, and no new cesspools are allowed.

   Sources: DOH 2017 cesspool priority report (poster)

The State’s newer prioritization tool (2022) ranks areas differently — Check My Property shows the current priority for your address. Every cesspool must be converted by 2050, wherever it is.