University of Hawaiʻi at Hilo researchers confirm sewage leaking into Keaukaha waters

A newly published University of Hawaiʻi at Hilo study reveals that sewage from cesspools and the Hilo Wastewater Treatment Plant is entering Keaukaha’s coastal waters faster than previously recorded.

The findings are the result of 2 years of research by UH-Hilo marine scientists and students, who used dye tracer tests to track sewage movement. They stress that Hilo should be a top priority for cesspool conversion to prevent further contamination.

Hawai‘i County’s Department of Environmental Management is currently working on addressing issues with upgrading wastewater treatment plants and a state requirement to convert large-capacity cesspools to more environmentally friendly systems by 2050.

The project began after Keaukaha residents raised concerns about strong sewage odors and possible health risks from pollution.

Lead researcher and UH-Hilo graduate student Shayla Waiki focused her thesis on tracking sewage in Keaukaha.

“We found dye emerge at the shoreline every time,” said UH-Hilo marine science associate professor Steve Colbert. “And the water moved fast, one to two football fields [in length], including end zones, each day.”

Waiki is now a natural resources specialist with the Army National Guard and plans to apply to UH-Mānoa’s law school this year.

Using water samples and the “Pilau-meter,” a public reporting tool for bad smells at Puhi Bay, researchers confirmed what the community suspected — sewage is present, and it’s traveling through groundwater quickly.

Pilau is the Hawaiian word for stink, rotten, foul.

Keaukaha, home to Hilo’s sewage treatment plant, also has numerous cesspools near the shoreline. Wastewater from these systems can introduce harmful bacteria and pollutants into coastal waters, raising concerns about infections such as methicillin-resistant Staphylococcus aureus, or MRSA, among residents.

The study’s findings are already driving action.

“Results from this research have been shared with the community and Hawaiʻi County, and are being used by the county to help prioritize locations for sewer line expansion in Hilo as part of the statewide effort to transition away from cesspools,” said Tracy Wiegner, a marine science professor at UH-Hilo who co-authored the study.

The study was a collaboration between UH-Hilo faculty and students, including former graduate students Joseph Nakoa and Devon Aguiar, and marine science undergraduates Nicolas Storie and Ashlynn Overly.

They are continuing environmental work in doctoral programs and conservation efforts throughout Hawaiʻi.

UH-Hilo marine science undergraduates Darienne Kealoha, Kaitlin Villafuerte, Finn Reil and Brooke Enright along with tropical conservation and environmental science graduate student Walter Boger also contributed to the study.

Other co-authors include UH-Hilo marine science professor Karla McDermid, UH-Mānoa Hawaiian studies associate professor Noe Puniwai and UH-Mānoa oceanography professor Craig Nelson.