A study published by University of Hawai'i at Mānoa earth scientists showed that tidally-driven groundwater inundation of wastewater infrastructure is occurring in urban Honolulu, Hawai'i.
The team studied coastal ocean water and storm drain water in low-lying areas during spring tides. Researchers used chemical tracers to detect groundwater discharge and wastewater present at each site, reported University of Hawai'i News.
The study was led by postdoctoral researcher Trista McKenzie and co-authored by UH Sea Grant coastal geologist Shellie Habel and Henrietta Dulai, advisor and associate professor in the UH Mānoa School of Ocean and Earth Science and Technology, reported University of Hawai'i News.
According to the study, the study shows that higher ocean water levels are leading to wastewater entering storm drains and the coastal ocean, reported University of Hawai'i News. This creates negative impacts to coastal water quality and ecological health.
"Our results confirm that indeed, both groundwater inundation and wastewater discharge to the coast and storm drains are occurring today and that it is tidally-influenced," said McKenzie, according to University of Hawai'i News. "While the results were predicted, I was surprised how prevalent the evidence for these processes and the scale of it."
In low-lying inland areas, storm drains can overflow every spring tide and at the same time wastewater from compromised infrastructure also discharges into storm drains, according to the study, reported University of Hawai'i News.
In turn, during high tides storm drains can become channels for untreated wastewater to flood streets and sidewalks.
The team also discovered that many human-derived contaminants were in concentrations that pose a high risk to aquatic organisms, which negatively impacts coastal organisms where the groundwater and storm drains discharge, reported University of Hawai'i News.
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