Sewage enters Puakō groundwater, says UH, sewage treatment plant is needed


Studies of dye tracers with sumps and septic tanks show that the sewage reaches the shore within hours. Photo courtesy of University of Hawaii.

(BIVN) – Researchers say sewage is entering Puakō’s groundwater and recommend a sewage treatment plant for the coastal village of western Hawai’i.

A team from the University of Hawaii at Hilo is studying the impact of local sewage systems on coastal water quality and has published their recent findings in the Journal of Hydrology: Regional Studies. Researchers conducted dye tracer studies at Puakō to determine the hydrological connection of sumps, septic tanks, and aerobic treatment units to coastal waters, and found that the dye emerged rapidly from riparian sources within six hours.

“If you went to the toilet at high tide when you flush the toilet, the sewage would flow to the shore at low tide,” said Steve Colbert, professor of marine science at UH-Hilo. “And this is not the kind of water I would like to swim in and it also has implications for the health of our coral reefs.”

Extract from a press release from the University of Hawaii:

Data collection over the past few years has shown bacteria levels on the Puakō coast to be higher than Hawaii Department of Health standards in recreational waters facing 81% of the residential homes sampled. .

The research team, led by UH marine science professors Hilo Tracy Wiegner and Steve Colbert, also found that bacteria levels were high regardless of the type of sewage disposal system on site, sump, septic tank or aerobic treatment unit used by the home.

The researchers concluded that without a wastewater treatment plant, 69% of the sampled area would not meet Ministry of Health water quality standards, even if every resident switched to new sewage systems. “From a water quality perspective, both with regard to human health and that of the coral reefs, Puakō is building its own [sewage treatment plant] would be best, ”the researchers said in their published work.

Shore of Puakō. Photo courtesy of University of Hawaii.

Working with the community

The research team’s involvement with the community of Puakō followed a ban on construction of new sumps in 2015 due to concerns about threats to human health and that of coral reefs. In 2017, state laws were changed to require all sumps to be replaced by 2050.

“The Puakō community association has let us know that they are looking to abandon the sumps,” 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 determine where the sewage was entering the groundwater in the Puakō watershed.

According to Wiegner and Colbert, the community is considering three options: replace the sumps with aerobic treatment units, build a sewer line to the sewage treatment plant at Mauna Lani Resort, or build a treatment center in Puakō.

“We’re really not the funniest people to go to the beach with,” Colbert said. “[But] the community has been so supportive of our work, helping us access sites and attending community meetings where we shared our results.

Puakō houses along the shore. Photo courtesy of University of Hawaii.

Difficult location

Puakō is particularly vulnerable to changes in sea level because there is not much distance between the surface of the ground and where the water is below. This coastline has one of the highest bacterial concentrations on the island of Hawai’i.

“You have a main road and houses on either side,” Wiegner explained. “There are houses a few feet from the ocean and near tidal pools.”

The extent of sewage pollution increases in areas with limited soil, facilitating bacterial treatment.

UH Hilo faculty and students collect data. Photo courtesy of University of Hawaii.

Known consequences

Wastewater is made up of a sludge of potentially dangerous pathogens, nutrients, cleaning chemicals, hydrocarbons, and pharmaceuticals. It presents risks to human health which can lead to abdominal, skin, urinary and blood infections.

The state’s health department publicly reports levels of dangerous bacteria in water quality advisory reports posted on its Clean Water Branch System website.

Consistently high concentrations of wastewater on reefs can stimulate bioerosion, decline in reef diversity, high disease prevalence and severity, changes in species distribution and loss of diversity in coral communities.

Student performing tests in the laboratory. Photo courtesy of University of Hawaii.

Provide data to lawmakers

Water quality data was collected by sampling water from groundwater wells at Puakō, Waikoloa Village, and Mauna Lani, and from the shores of resorts in Mauna Kea, Hapuna Prince (now Westin Hapuna Beach Resort) , Fairmont Orchid and Mauna Lani.

Wiegner said she was happy to provide lawmakers with information relevant to community requests to improve pollution control in their coastal waters.

In 2019, the Hawaii State Legislature allocated $ 1.5 million in capital improvement project funds for the planning and design of a wastewater treatment plant in Puakō.

Hawai’i County provided $ 250,000 in matching funds and levied state contributions to advance the planning and design of a wastewater treatment plant in Puakō.

Dedicated teamwork

Wiegner attributes the study’s positive impact to teamwork alongside Colbert and UH alumni Hilo Leilani Abaya and Jazmine Panelo, UH Mānoa associate researcher Craig Nelson and graduate student from UH Mānoa Kristina Remple.

In addition to the Puakō Community Association, other partners include Coral Reef Alliance, The Nature Conservancy, South Kohala Coastal Partnership, Fairmont Orchid Development, Mauna Kea Resort, County of Hawai’i Department of Water Supply, and UH Mānoa.

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