Lahaina Injection Wells Release Wastewater to Coast, Tests Find

posted in: February 2012 | 0

The long wait has ended. Researchers have now verified what many people had suspected for years: wastewater from the Lahaina sewage treatment plant, on Maui’s Ka`anapali Coast, is reaching coastal waters.

Starting in late July, scientists with the University of Hawai`i injected copious amounts of fluorescein dye – 340 pounds of it – into two of the wells used by Maui County to dispose of treated wastewater at the Lahaina plant.

That was followed on August 11 by the injection of 180 pounds of rhodamine dye into a third injection well, which lies further mauka.

By putting dye into the wastewater, the researchers were seeing if they could confirm suspicions that it was reaching – and possibly contaminating – coastal waters. Those suspicions, going back more than two decades, were heightened in 2010. That year, two serious scientific studies were published that reported finding in coastal seeps downstream of the injection wells the type of chemical and biological profiles typically associated with wastewater. (For a full account of these studies, see the May 2010 issue of Environment Hawai`i.)

For Maui County, the reports could not have come at a worse time. The county was seeking to renew permits for the Lahaina injection wells, and the U.S. Environmental Protection Agency was considering whether to require the plant to obtain a National Pollutant Discharge Elimination System (NPDES) permit for it as well, given the apparent connections between the injection wells and the ocean.

The county protested that the studies were speculative and that no definitive link was established between the injection wells and the coastal seeps. The EPA backed off, agreeing to allow the dye tests to go forward and to require the county, in the meantime, to ramp up chlorination of the injected wastewater.

A Long Vigil

For the first month following the dye injection, sampling along the coastal seeps was done twice a day, according to people involved with the tests. After a month, that slipped to daily or every other day.

On October 6, Gary Gill, deputy director of the Department of Health, said at a University of Hawai`i seminar that although “gobs and gobs” of dye had been injected, “nothing’s come up in the coastal area.”

But the sampling of submarine springs continued, and, before the month was out, samples at some of the locations began to show elevated levels of fluorescein.

“That concentration – above the baseline levels, which told the researcher something significant is going on – has continued to rise and is now very clearly present,” said David Albright, manager of the groundwater and underground injection control program for the EPA’s Region IX, in San Francisco. “

The rhodamine dye had not yet turned up by mid-January, but Albright explained that the well into which the rhodamine dye had been placed was about a hundred yards further inland than the two wells receiving the fluorescein. “We expected it would take longer [for the rhodamine to show up], since it had to travel further,” he said in a telephone interview with Environment Hawai`i.

Do the long delays between the injection of the dyes and their detection at the coast give researchers an idea of the travel time required for wastewater to meet the coast, Albright was asked.

At this point, he replied, “certainly it’s an indicator of travel time for something, but I wouldn’t say that since the dye took this long, the injection fluid does as well.”

Permitting

Albright would not say whether the EPA would now be requiring the county to obtain an NPDES permit for the injection wells. “The detection of fluorescein confirms that there’s a connection [between wells and ocean],” he said.

“But is that a trigger for an NPDES permit? I’d say it’s too early to say. We need to get a sense of travel time, a sense of what is being discharged. That will be important, and that monitoring is only now starting to occur.”

The Department of Health, he continued, is starting to monitor seeps for bacterial indicators, nutrients, and a number of other standard wastewater constituents. “Thus far, the data that have been collected – very preliminary, at least for pathogens – are negative, showing none of the bacterial indicators they’ve sampled for.”

Albright acknowledged, however, that the failure to detect bacterial indicators of wastewater might be linked to the increased chlorination at the plant, which began in early October. “Pursuant to the agreement worked out between the EPA and the county,” he said, “they’ve increased the level of chlorination to what would be R-2 level wastewater.”

Warmer Water

Another area of research that has shown results, Albright said, was an infrared thermal survey of the West Maui coast. That, he said, “involved flying over the area, using sophisticated instruments to measure a thin layer of surface water for temperature variations.”

The instruments were highly sensitive and accurate, and could detect very small variations in the surface water temperature, he continued.

“What they saw with the data they collected was a sizable plume of warmer water around the seeps,” he said. The finding was confirmed in direct measurements of the temperature of water coming out of the seeps, where the temperatures were on the order of one to two degrees Centigrade higher than the surrounding ambient ocean water.

Groundwater is usually cooler than ocean water, so the fact that the seeps discharge warmer water also tends to confirm the presence of wastewater.

The researchers also looked at isotopes of nitrogen in the samples taken from the seeps. The results, said Albright, “were consistent with the findings of Chip Hunt and Megan Dailer,” the principal authors of the two earlier studies. “Waters that migrate to the coast from the [wastewater] facility and upgradient wells are undergoing significant microbial nitrate reduction.”

“Ambient ocean water has next to no nitrates,” he said.

Patricia Tummons

Volume 22, Number 8 — February 2012

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