If you have looked up your property, you may have seen a short line that says Priority 3 and felt a small wave of relief. Priority 3 sounds like the back of the line. Lower risk, later problem, maybe somebody else’s problem.
That is a reasonable way to read a number. It is also mostly wrong. Here is what the number actually is, where it comes from, and what it does and doesn’t change for you.
What the State is actually measuring
Start with what a cesspool is. It is not a treatment system. It is a hole in the ground that wastewater drains into, and after that, gravity does the rest. On Hawaiʻi Island the ground under that hole is usually young, cracked lava rock, which lets water through quickly. Whatever leaves your toilet soaks down to the groundwater and travels with it toward whatever lies downhill: a drinking-water well, a stream, a bay.
- Toilet
- Cesspool
- Lava rock
- Groundwater
- A well, a stream or the ocean
The Hawaiʻi Cesspool Prioritization Tool, built by the University of Hawaiʻi Water Resources Research Center with the State Department of Health, asks a simple question about that path: how short is it, and what is waiting at the end? It lays every known cesspool over fifteen statewide layers of data and weighs each one by how much it matters to people and the environment.
Those layers are the physical facts you would want to know about any cesspool. How far it is from the coastline. How far it is from public and private drinking-water wells. How deep the groundwater sits beneath it. Whether it is inside the area the State expects sea-level rise to reach by 2050, where rising groundwater can flood a cesspool. The data behind the tool also records whether a cesspool sits inside a public well’s capture zone, the area the Department of Health maps around a well to protect drinking water. In Zone B, groundwater can reach the well within about two years; in Zone C, within about ten.
The results, using 2022 data, are grouped by census tract into three tiers. Priority 1 is the highest combined risk, Priority 2 is high, and Priority 3 is lower relative risk. Notice the word relative. A tier compares neighborhoods with each other across the whole State. It does not say any cesspool is harmless.
Where Hawaiʻi Island lands
- cesspools on Hawaiʻi Island (State prioritization tool, 2022 data)
- about 48,600
- cesspools on Hawaiʻi Island (State prioritization tool, 2022 data)
- of them in Priority 3 tracts, including all of Puna, Kaʻū and Hāmākua (same tool)
- 84%
- of them in Priority 3 tracts, including all of Puna, Kaʻū and Hāmākua (same tool)
- the one legal deadline, for every tier (HRS §342D-72)
- 2050
- the one legal deadline, for every tier (HRS §342D-72)
The tool counts about 48,600 cesspools on the island, spread across 33 census tracts. Just three tracts, with about 5,100 cesspools (11%), are Priority 1: Kailua-Kona, Hōlualoa, and Kawaihae–Waikoloa. Five tracts, with about 2,600 cesspools (6%), are Priority 2: Keaukaha–Panaʻewa, Villa Franca–Kaikoʻo and University–Houselots in Hilo, plus Kealakehe and Kaumalumalu–Keauhou in Kona.
Everything else, 25 tracts and about 40,900 cesspools, is Priority 3. That includes all of Puna, Kaʻū and Hāmākua, and most of Hilo. The top of the list sits mostly along the Kona and Kohala coasts, where porous rock, dense development and heavily used nearshore water all meet, plus a handful of Hilo neighborhoods. If you live almost anywhere else on the island, you are Priority 3. You are in the large majority.
Why Puna is the case to think about
In 2017 the Department of Health published a different list, naming five Hawaiʻi Island areas of concern. It ranked the Keaʻau–Puna corridor highest on the island. About 9,300 cesspools, roughly 17 percent of all the cesspools in Hawaiʻi, are packed into a corridor about 4.3 miles wide on Kīlauea’s east slope, along the path groundwater flows. There is little to no soil to slow anything down; University of Hawaiʻi research found wastewater can reach the water table in a fraction of an hour.
Much of that area has no public water system, so many households drink from private wells or rain catchment. When the Department of Health sampled domestic wells there, it found wastewater indicator bacteria in a quarter of them.
In the 2022 tool, most of Puna is Priority 3. The newer tool uses a different method and scores larger areas, so a place with real, measured problems can still land in the lowest tier. Both things are true at once. You can read about all five 2017 areas in Why Hawaiʻi Island.
A priority tier ranks neighborhoods against each other. It doesn’t measure what’s under your house.
Does my tier change my deadline?
Not today. State law sets one deadline for every cesspool in every tier: January 1, 2050. In 2022 the Cesspool Conversion Working Group recommended earlier dates, 2030 for Priority 1 and 2035 for Priority 2, but those were never enacted. Bills to change the deadlines come up most sessions, in both directions, so it is worth keeping an eye on. There is also no requirement to convert when you sell.
So does priority matter? Sometimes, yes. That does not mean it sets your schedule. Where it has mattered is money. The State’s pilot grant program, which ended in 2024, paid up to $20,000, and past State assistance focused on Priority 1 and 2 areas. Right now there is no State grant and no Hawaiʻi County grant. The only new program is the Act 204 (2026) revolving loan fund, run through the Hawaiʻi Green Infrastructure Authority, which isn’t taking applications yet. If rules do tighten someday, the Working Group’s recommendations suggest they would tighten first where the tier is highest.
So, can you relax?
A little. If you are Priority 3, there is no earlier deadline hanging over you and no reason to panic. If you are Priority 1, there is no reason to panic either; your legal deadline is the same. What is worth your attention is not the tier but the facts about your own cesspool.
How far is it from the ocean? How deep is the groundwater? Is there a drinking-water well nearby, or a capture zone around one? A Priority 3 home a few hundred feet from the shore, over shallow groundwater, has more in common with Puakō than with a Priority 3 home far upslope. At Puakō, a University of Hawaiʻi at Hilo dye study of shoreline homes found flushed wastewater reaching the ocean in as little as six hours, and within ten days at most.
The sane plan is the same in every tier. Know your tier, and know your surroundings. Understand that a licensed engineer’s site evaluation, not a census-tract score, decides what system fits your lot. And check back after each legislative session, because the rules around funding and deadlines are still moving.
The priority tier comes from public State data and is for general information. It isn’t an official determination about your property.
Priority tells you where the State will look first. Groundwater doesn’t wait to be looked at.
If you want to see your own numbers, Check My Property shows your property’s priority area and what is around its cesspool: the distance to the ocean, the depth to groundwater, and any nearby wells. It takes about a minute.
