Scientific findings from a study by University of Hawaii at Manoa helped the U.S. Supreme Court decide in April that a Maui sewage plant must comply with the Clean Water Act.
In a news release, the university reported that researchers from the School of Ocean and Earth Science and Technology mapped the spread of the effluent from a municipal wastewater treatment plant on Maui to coastal waters.
They found that millions of gallons of “deeply injected treated sewage” from the West Maui wastewater reclamation facility in Lahaina were finding their way to ocean waters near Maui every day.
“This was a very impactful scientific study with regard to protecting the environment, and with far-reaching, socio-economic and sustainability implications for the State of Hawaii and the nation as a whole,” said Craig Glenn, lead author of the study and professor of earth sciences at SOEST, in the news release.
Researchers “collected thermal infrared imagery … deployed scuba seafloor mapping, analyzed groundwater and algae samples to look for isotopic signatures unique to wastewater, used radioisotopes to help establish flow rates and deployed tracer dyes to track rates and paths of the injected wastewater effluent to Maui’s coastal waters.”
The tracer dye showed that wastewater travels through groundwater and into the ocean.
The study came after Maui coral reefs were observed to have experienced declining health and overgrowth by algae during the past decade. A growing concern was that the reefs’ health was being harmed by underground discharge carrying nutrients from wastewater.
Maui County had argued that it did not need to comply with the Clean Water Act to inject the treated sewage into the groundwater, but the university said that the study helped clarify to the U.S. Supreme Court that “underground water connections to surface waters are covered by the Clean Water Act.”
In its 6-3 vote, the U.S. Supreme Court ruled against Maui County as well as President Donald Trump’s administration, which had sought to loosen water pollution requirements.
The earth sciences researchers received grants from the U.S. Environmental Protection Agency and U.S. Army Engineer Research and Development Center to conduct the study.
