The town of Hauula packs hundreds of homes into a narrow strip of land sandwiched between verdant, towering cliffs of the Koolau mountain range and the Pacific. But the stunning views obscure an environmental problem beneath the ground.
This rural part of the island of Oahu is not connected to city sewers — and waste from toilets, sinks and showers is mostly collected in hundreds of pits called cesspools.
With climate change, rising seas are eroding Hawaii’s coast near homes with cesspools. Sea rise also is pushing the island’s groundwater closer to the surface, allowing the cesspool effluent to mix with the water table and flow into the ocean. And scientists say cesspool pollution may even percolate into streets and parks in low-lying former wetlands in the future.
"We want proper sanitation as much as anybody wants it. We don’t want our children swimming in an ocean of bacteria," said Dotty Kelly-Paddock, president of the Hauula Community Association. "It’s got to change."
Hawaii has 83,000 cesspools — more than any other state — and about 20% are less than 0.6 mile from shore. Six years ago, Hawaii mandated removal of all cesspools by 2050.
The task is daunting and costly, but scientists warn that problems from this unsanitary complication of island life will only be exacerbated by global warming.
Cesspools sprang up across Hawaii during years of rapid growth and now are everywhere from old sugar plantation towns to the posh Honolulu enclave Black Point.
Most homes with cesspools are in neighborhoods without sewers. In theory, the ground gradually filters bacteria and pathogens in effluent from them.
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But rising seas and more intense storms are encroaching on coastal properties, as happened last year when a house collapsed onto a beach along Oahu's North Shore surfing mecca. Some coastal erosion removes sand surrounding cesspools and pulls sewage out to sea.
Cesspools that are inland are sometimes so close to aquifers that sewage pollutes them and can travel through springs to beaches and the ocean.
When researchers placed dye in shoreline cesspools in the town of Puako on the Big Island for a 2021 study, it emerged in coastal springs only nine hours to three days later, said Tracy Wiegner, a University of Hawaii-Hilo marine science professor.
Researchers also found bacteria levels in the ocean exceeded state health standards in front of 81% of the Puako homes sampled.
Public health officials warn exposure to sewage can cause gastroenteritis, diarrhea, conjunctivitis and skin infections. A 2020 Hawaii Department of Health report said little is known about how bacteria and viruses are carried through waters in wet tropical regions where people swim year round, but it said Hawaii had twice the rate of difficult-to-treat superbug MRSA infections than the national average.
Environmental scientist Daniel Amato coordinates volunteers who test water quality at 24 sites across Oahu for the Surfrider Foundation every two weeks. He said it’s difficult to prove that cesspools are the source of the bacteria the team finds but bacteria levels are high where there are many cesspools.
