Preliminary results of injection well tracer study reveal low bacterial levels
HONOLULU – The U.S. Environmental Protection Agency last week released preliminary results from an ongoing investigation by federal and state agencies to evaluate the fate of effluent from the Lahaina Wastewater Reclamation Facility near the Kaanapali coast.
According to the interim report, one of two tracer dyes introduced in the wells was detected at the coastal seeps located roughly one-half-mile southwest of the Honokowai sewage treatment plant and between three and 25 meters from shore.
The dye detection establishes a hydrologic connection between the West Maui facility’s treated wastewater injection wells and the monitored submarine seeps.
The studies are inconclusive for detection of the second tracer dye, although data collection at the seeps continues.
While the report confirms a hydrologic connection between the injection wells and the near-shore seeps, monthly sampling of the seeps by the Hawaii Department of Health has detected no bacterial indicators.
In addition, DOH monitoring near the seeps indicates bacterial levels that are low or nonexistent, and well within the range considered safe for swimming.
In 2011, EPA required the County of Maui to increase its level of wastewater disinfection prior to injection.
In addition, the county is on schedule to meet EPA requirements to achieve full ultraviolet disinfection of all wastewater at the West Maui facility by December 2013.
“We now have a much better understanding of the movement of the wastewater injected in Lahaina,” said Jared Blumenfeld, EPA’s regional administrator for the Pacific Southwest.
“Although we continue to collect and analyze data, the findings underscore the need for EPA and the Hawaii Department of Health to consider any and all regulatory tools to ensure protection of public health and the marine habitat, including nearby coral reefs, in West Maui.”
“The results from DOH confirm that our ocean water is clean and safe,” said Maui County Mayor Alan Arakawa.
“The County of Maui, State of Hawaii Department of Health and the Environmental Protection Agency continue to work cooperatively to obtain the best science to inform our decisions, a process that is ongoing.”
It took just under three months for the tracer dye to first appear at the seeps, but the results suggest an average travel time from the injection wells to the submarine seeps in excess of seven months.
Additional key results include the temperature, salinity, pH, nutrient concentrations and discharge rate of the monitored submarine discharges.
Funded by the U.S. EPA, U.S. Army Corps of Engineers and the Hawaii Department of Health, the University of Hawaii has been studying the effluent flow from the plant’s injection wells to near-shore ocean waters since July 2011.
The researchers will continue to collect data from water samples from the identified discharge points through the end of 2012. They will also continue their data analysis and modeling to clarify the processes that affect the transport of the treated wastewater effluent and its eventual discharge into the marine environment.
A final report on the results of the tracer dye study is expected in June 2013. To see the interim report, visit www.epa.gov/region9/water/groundwater/uic-permits.html#lahaina.