Hawaii Private Well Water Quality 2026

The Red Hill Crisis — PFAS in Hawaii’s Aquifer

The defining water contamination event in Hawaii’s recent history began in November 2021, when a series of fuel releases at the Navy’s Red Hill Bulk Fuel Storage Facility — a World War II-era underground complex sitting just 100 feet above Oahu’s primary drinking water aquifer — contaminated the Navy’s water distribution system. Approximately 93,000 people on Joint Base Pearl Harbor–Hickam and surrounding military housing areas were impacted, many of whom were forced to relocate during the crisis.

The fuel contamination was serious enough — but the PFAS dimension of Red Hill has proven equally alarming. In early 2024, the EPA and Hawaii DOH found PFAS contamination in the soil and groundwater surrounding the Red Hill facility. Of 21 monitoring wells tested around Red Hill in September 2023, 6 showed PFAS levels exceeding EPA screening standards — most significantly PFOS exceedances near the Red Hill Shaft. It is important to note that these are monitoring wells used to track groundwater conditions, not drinking water wells; however, the contaminated groundwater lies in the same interconnected aquifer that the Navy and civilian water utilities rely on for drinking water supply. The contamination originates from Aqueous Film Forming Foam (AFFF) — a firefighting chemical used at the facility — with additional PFAS sources including legacy oily waste disposal operations dating back to the 1940s. A federal inspector general report published in November 2024 found that the Navy failed to properly report multiple AFFF spills to state and federal regulators.

The Navy defueled the Red Hill tanks by March 2024, removing over 104 million gallons of fuel. But the remediation of the underlying PFAS and petroleum contamination is expected to take decades. The Honolulu Board of Water Supply is still detecting fuel-related contamination in city-owned drinking wells across Leeward Oahu and is actively installing granular activated carbon (GAC) treatment systems at its Ka’amilo Wells to address PFAS detections. BWS estimates the total cost of past, current, and future impacts from the Red Hill fuel leaks at $1.2 billion.

For private well owners near the Aiea, Halawa Valley, and Pearl Harbor areas of Oahu, this is not a distant public utility problem — it is a direct threat to their groundwater. The contamination plume is moving in a westerly direction through the aquifer. The Navy’s own monitoring wells and BWS monitoring systems are both tracking its spread.

The Cesspool Crisis — 83,000 Untreated Sewage Sources

Hawaii has a second, less headline-grabbing water contamination crisis that directly affects private well owners across every island: cesspools. The Hawaii Department of Health estimates there are approximately 83,000 cesspools statewide — the EPA uses a slightly higher figure of around 88,000 — discharging approximately 53 million gallons of untreated sewage into the ground every single day, according to the DOH Wastewater Branch. Because groundwater provides approximately 95% of all domestic water in Hawaii, cesspools represent a direct and ongoing threat to well water quality throughout the state.

A cesspool is essentially a hole in the ground where raw, untreated wastewater is deposited in direct contact with soil and groundwater. Unlike septic systems, cesspools provide zero treatment. Pathogens including bacteria, viruses, and parasites pass directly into the ground. A DOH and University of Hawaii study of private drinking water wells in Hawaiian Paradise Park on Hawaii Island sampled 32 wells and found approximately half positive for total coliform bacteria — with a quarter testing positive for E. coli specifically. This is a direct consequence of the area’s high concentration of cesspools contaminating the shallow aquifer.

Nitrate contamination from cesspools is also a documented problem. A 2018 DOH study of Upcountry Maui, where there are over 7,400 cesspools, found elevated nitrogen levels in the groundwater — a risk factor for blue baby syndrome in infants and associated with higher rates of certain cancers in adults.

Hawaii’s legislature passed Act 125 in 2017, requiring all cesspools to be upgraded, converted, or connected to a sewer system by January 1, 2050. But the conversion deadline is 2050 — meaning for the next 25 years, the vast majority of Hawaii’s 83,000 cesspools will continue discharging untreated sewage into the same aquifer that supplies most of the state’s drinking water.

Agricultural Contamination and Other Risks

Hawaii’s agricultural history has left a legacy of chemical contamination in groundwater across several islands. Decades of pineapple and sugarcane farming involved heavy pesticide and herbicide use on highly porous volcanic soils. Chemicals including DBCP (dibromochloropropane) and EDB (ethylene dibromide) — both now banned but persistent in groundwater — have been detected in wells on Oahu and Maui. Nitrate from fertiliser application continues to be a concern in active agricultural areas, particularly on the Big Island and Maui.

Hawaii’s volcanic geology also creates specific contamination pathways that are not present on the mainland. Lava tubes and porous basalt allow surface contaminants to move rapidly into the basal aquifer with very little natural filtration. What takes months or years to reach groundwater on the mainland can percolate into Hawaii’s aquifer in days. This makes Hawaii’s groundwater particularly vulnerable compared to states with thicker clay or sediment layers above the water table.

Regulatory Situation for Hawaii Well Owners

Private residential wells in Hawaii are not regulated under the federal Safe Drinking Water Act or its state equivalent. The Hawaii Department of Health Safe Drinking Water Branch has no authority to require testing of private wells. There is no notification system for well owners near contamination events, and no mandatory reporting of well test results.

Hawaii does have its own state PFAS maximum contaminant levels. Unlike many states that have no state-specific PFAS standards, Hawaii’s DOH established MCLs for PFAS in public water systems. However, as with the federal standards, these apply only to regulated public water systems — not private wells. Testing and treatment of your own well remains entirely your responsibility.

Check our Hawaii municipal water quality page for island and city tap water data, our Honolulu water quality page for Oahu-specific public system data, or use our live boil water notice tracker for active advisories across the state.

Known High-Risk Areas in Hawaii

If you live near any of the following locations, well water testing is urgent — not precautionary.

How to Test Your Hawaii Well Water — and What to Do Next

Given Hawaii’s contamination profile — military PFAS, cesspool-driven bacteria and nitrate contamination, and legacy agricultural chemicals — every private well owner in the state should test their water regardless of location. Hawaii’s volcanic geology means contamination can travel to the water table faster than almost anywhere else in the US. Annual testing for bacteria and nitrate is the minimum; PFAS testing is strongly recommended for any well on Oahu and for wells near former industrial or military sites on other islands.

Contact the Hawaii DOH Safe Drinking Water Branch at (808) 586-4258 for a list of certified laboratories. For Oahu wells near the Aiea-Halawa-Pearl Harbor corridor, request a full PFAS panel and petroleum hydrocarbon screen as a priority. For wells anywhere near cesspools — which in practice means most rural Hawaii — bacteria and nitrate testing should be annual.

For filter options, our well water filter guide covers reverse osmosis systems for PFAS and nitrate, UV disinfection for bacteria, and whole-house well systems for comprehensive treatment. You can also browse our full water filter solutions page or check your ZIP code for local water quality context.

For other well water risks by state, see our pages on Ohio wells and Michigan wells. Return to the private well water directory to find your state.