Sulfide levels in island canals near dewatering zones are high, but “not that severe” said Jon Iglehart, South District director for the Florida Department of Environmental Protection.

Tests run on water samples at a discharge point last week reveal that the canal contained levels of sulfides that are considered dangerous to freshwater shrimp, but not necessarily to saltwater organisms. Albert Walton, the specialist who gathered the samples from a canal near Maywood Court, sent the information about freshwater shrimp to Iglehart in an e-mail Wednesday.

Iglehart said his department is looking for information on levels that would be harmful to marine life, but he noted that saltwater organisms generally have a higher tolerance for chemicals.

Freshwater shrimp and larvae, of the species Macrobrachium rosenbergii, are often considered the canary in the coal mine when it comes to detecting unsafe levels of sulfides in bodies of freshwater, Iglehart said.

DEP Environmental Manager Jennifer Nelson said that the department has observed no “organism mortality,” and that she does not foresee any human health risk.

“From what I see there appears to be no human health hazard whatsoever,” Nelson said. “This is a gas that’s dissolved in the water, so if you’re swimming in the water the impact would be more if you breathed it in. What we’re concerned about is these little critters who live in the water.”

The water measured just downstream from the discharge point registered 5.3 milligrams of sulfide per liter, a level Walton wrote would be “toxic” to freshwater shrimp. The level at the discharge point was .8 milligrams per liter, a lower level, but one that “would not be safe for them.”

A canal with no dewatering registered a level of .05 milligrams of sulfide per liter, the same level found to be acceptable by Australian Drinking Water Quality Guidelines, Walton wrote in his e-mail.

Photo by QUENTIN ROUX

Eagle staff

Albert Walton, a biologist with the Department of Environmental Protection based in Punta Gorda, closes the top on a bottle of water removed from a ground dewatering discharge site on Mayfield Court on Marco Island. Walton said the samples he took would be sent to Tallahassee for analysis, and that the results should be available within a few days.

Sulfate levels were also high at the discharge point, but not enough so to cause alarm. Sulfur has been named as one possible source of the “rotten eggs” odor on the island that has commonly been attributed to hydrogen sulfide.

Walton also wrote that the elevated levels dissipate rapidly within 20 or 25 meters, roughly two lots away from where the measurements were taken.

“Based on what we have so far, any water quality impacts on the biological community are very localized,” Nelson said.

Iglehart said the pattern of quick dispersal leads him to believe that the problem can be rectified through a solution such as more careful filtration, and that the concerns would not halt construction.

“But we are concerned because these levels have been shown to be toxic to aquatic organisms,” he said. “We are going to try to find a method for construction to continue without releasing these levels.”

Iglehart will join Marco Island officials and construction contractors today for a teleconference to discuss ways to manage the sulfide concentrations in the pumped groundwater.

As of Wednesday at press deadline a time had not yet been set for the meeting, but Public Information Coordinator Lisa Douglass said the meeting will not be open to the public.

With these results, more tests may be in order, Iglehart said, in order to measure turbidity levels at other discharge areas on the island.

Turbidity, a clouding of the water, is often the result of too much fine sand in discharged water. Iglehart said it can have a smothering effect on marine life.

“When you pump water out of the ground you generally get a first flush of cloudy water, and that is a concern to us,” Iglehart said.

He said there was no turbidity measured in the samples taken at Maywood Court last week, but that it could be a problem at areas just beginning to undergo dewatering.

“So we would need to find a way to deal with that with contractors on site,” Iglehart said.

He said the tea-like hue of water pumped at discharge points is not cause for alarm though, because the water gets its pigmentation from naturally occurring tannins in leaves and other organic matter.

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