What happens during a sewage spill, how to check if your beach is affected, and how long to wait before swimming.
A sewage spill (also called a sanitary sewer overflow or SSO) occurs when untreated or partially treated wastewater escapes from the sewer system into the environment. In Hawaiʻi, these spills often reach streams, storm drains, canals, and ultimately the ocean — contaminating the water at nearby beaches with dangerous bacteria and pathogens.
Spills range from minor (a few hundred gallons from a broken pipe) to catastrophic (millions of gallons during major infrastructure failures or storms). The 2021 Honolulu sewage spills sent hundreds of millions of gallons into the Ala Wai Canal and nearshore waters, closing beaches for weeks.
The most frequent sewage spills occur in urban Honolulu. The Ala Wai Canal watershed, which drains into the ocean near Waikīkī, has a documented history of major sewer overflows. The city's aging infrastructure serves nearly a million residents. Mānoa, McCully, and surrounding neighborhoods are frequent trouble spots.
Kahului and central Maui have experienced sewer spills from aging infrastructure. The Lahaina area has had documented wastewater issues, including injection well contamination reaching the ocean.
Less frequent due to lower population density, but spills do occur. Heavy rain events can overwhelm smaller sewer systems. Areas with limited sewer infrastructure rely more on cesspools, which have their own chronic contamination issues.
If you hear about a sewage spill anywhere near your beach, stay out of the water until DOH gives the all-clear. Sewage contamination can spread further than expected via ocean currents. The health risks from swimming in sewage-contaminated water are serious and not worth the risk.
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⚠️ Important Disclaimer
Safe to Swim Hawaii is an independent passion project — not affiliated with the Hawaii Department of Health or any government agency. Information is for educational purposes. Not real-time measurements.
Always verify conditions with the Hawaii DOH Clean Water Branch.
When in doubt, don't go out. 🤙