East Hawaii News

Puakō Sewage Runoff Leads to Treatment Plant Recommendation

December 12, 2021, 11:30 AM HST
* Updated December 12, 11:19 AM
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Researchers at the University of Hawai‘i at Hilo are recommending that a wastewater treatment plant be constructed in Puakō.

The research team studied the impact of local sewage systems on coastal water quality and determined that the community is in great need of a treatment facility. Dye tracer studies were conducted to determine the hydrological connection of cesspools, septic tanks and aerobic treatment units to nearshore waters.

The research team found the dye rapidly emerged from shoreline springs within six hours. Their findings were recently published in Journal of Hydrology: Regional Studies.

“If you went to the bathroom at high tide when you flush the toilet that sewage would be coming out to the shoreline at low tide,” said Steve Colbert, a professor of marine science at UH-Hilo. “And it’s not the kind of water that I would want to be swimming in and it also has implications for our coral reef health.”

Dye tracer studies with cesspools, septic tanks show sewage flow reaches shoreline within hours. PC: University of Hawai❛i at Hilo

Data collection during the past several years showed bacterial levels on the Puakō coastline were higher than state Department of Health standards in recreational waters fronting 81% of residential homes sampled. The research team, led by Colbert and fellow UH-Hilo marine science professor Tracy Wiegner, also found that the bacterial levels were elevated regardless of the type of onsite sewage system homes used.

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The researchers concluded that without a wastewater treatment plant, 69% of the area they sampled would be out of compliance with Health Department water quality standards even if every home upgrades to new sewage systems.

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“From a water quality standpoint, both in regards to human and coral reef health, Puakō building its own (sewage treatment plant) would be best,” stated the researchers in their published work.

The research team’s involvement with the Puakō community followed the 2015 ban of construction of new cesspools because of concerns about threats to human and coral reef health. In 2017, state laws were changed to require all cesspools be replaced by 2050.

“Puakō Community Association expressed to us that they were looking to transition away from cesspools,” Wiegner said. “We wanted to help understand the reality of each of these options. We went north, south and up the mountain to three different communities to figure out where sewage was entering into the groundwater in Puakō’s watershed.”

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According to Wiegner and Colbert, the community is considering three options: Replacing cesspools with aerobic treatment units, building a sewage line to the Mauna Lani Resort wastewater treatment plant or building a treatment center in Puakō.

Puakō is particularly vulnerable to changes in sea level because there is not much distance from the surface of the ground to where water sits below it. The community’s shoreline has one of the highest bacterial concentrations on Hawaiʻi Island.

“You’ve got a main road and houses on either side of it,” Wiegner said. “There are homes just feet away from the ocean and near tide pools.”

The magnitude of sewage pollution increases in areas where there is limited soil, which aids in bacterial processing.

Sewage is composed of a slurry of potentially hazardous pathogens, nutrients, cleaning chemicals, hydrocarbons and pharmaceuticals. It poses human health risks that can lead to abdominal, skin, urinary and blood infections.

Consistently elevated concentrations of sewage on reefs can stimulate bioerosion, decline of reef diversity, high disease prevalence and severity, shifts in species distributions and loss of coral community diversity.

Water quality data was collected by sampling waters from groundwater wells at Puakō, Waikoloa Village and Mauna Lani, and from resorts’ shorelines at Mauna Kea, Hapuna Prince (now Westin Hapuna Beach Resort), Fairmont Orchid and Mauna Lani.

In 2019, the Hawai‘i Legislature allocated $1.5 million in capital improvement funds for the planning and design of a wastewater treatment plant at Puakō. Hawai‘i County also provided $250,000 in matching funds and encumbered the state’s contributions in order for the planning and design of a facility in Puakō to move forward.

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