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In response to a strong odor often attributed to hydrogen sulfide, the city shut down dewatering pumps at the construction site of a sewer lift station on Granada Court on Tuesday afternoon.

Granada Court is located in the southeastern area of the island, near the intersection of San Marco Road and North Barfield Drive. City officials were allowing the water to be discharged into open swales there, while it had stopped elsewhere, because they believed the area being dewatered was small enough to limit any ill effects.

Most areas in need of dewatering are divided into sections of about 1,000 feet. Under the direction of ENVIRON, the firm called in to monitor hydrogen sulfide in city air, the city decided that the sheer size of some areas was leading to the high output of the gas.

However, they reasoned that the limited area requiring dewatering for a lift station would not lead to any problems.

“It’s a small area in comparison to well-point dewatering that is taking place for the sewer lines,” City Manager Bill Moss said at a Sept. 28 meeting. “We will transport (the removed water) directly into the canals. I think most would agree that has not been a problem.” Continued dewatering at the lift station site was part of a council-approved action plan that called for its suspension elsewhere — with the exception of North Barfield Drive, where water was pumped directly into a sanitary sewer force main.

Installation of sewers in that area has since been completed, said city Project Engineer Jim Miller. Construction crews are now wrapping up work in the district and restoring the roads and sidewalks torn up through the process.

City Council members Terri DiSciullo and Chuck Kiester visited the Granada Court site Tuesday and called city staff to shut the pump down because they picked up what Kiester called a “powerful” odor of rotten eggs in the area. The smell, often attributed to sulfur, is also associated with hydrogen sulfide.

“It was pretty bad,” Kiester said. “I came away with a headache.”

Moss said his staff didn’t pick up any smell when they went to the site, but he chose to act quickly and shut the pump down regardless.

“Most of us thought that area where the lift station is being built is not a dredge and fill area,” Moss said. “But rather than question it, we decided to just go ahead and shut it down.”

Hydrogen sulfide levels are believed to be higher in dredge and fill areas because of the presence of more decaying mangrove trees under the ground’s surface. Hydrogen sulfide naturally results from the breakdown of organic materials.

Now, the city will revert to pumping the removed groundwater into a force main, mimicking the process employed on North Barfield Drive.

However, hope may be in sight for the contentious Septic Tank Replacement Program, which has had a halting journey, particularly over the last two months, with allegations by residents of hydrogen sulfide-related illness.

Moss said the city has identified a mobile water treatment system that may be the answer to the sewer program’s hydrogen sulfide problem. The trailer-mounted units will arrive on the island in one to two weeks, Moss said, in time for the ENVIRON scientists to return to the island and test its efficacy at removing the gas from displaced groundwater.

The city will lease the system from Heyward Incorporated, a Maryland-based company with sales offices in Winter Park, Fla., Miller said. If tests reveal that it is effective, Moss said, the monthly $8,000 lease could get absorbed into the $55,000 purchasing price of the machine.

“We didn’t want to make that full investment until we set it up and bring ENVIRON back to test it,” Moss said.

However, DiSciullo sent an e-mail to Moss Wednesday questioning the decision by city staff to lease the system without first submitting plans to council for approval.

“If it is decided by council to purchase this equipment, what account do you propose to charge it to? The STRP project? The total rate base? Operating contingency?” she asked. “I don’t think we should be going about this piecemeal. We should have a plan set out before us to approve or disapprove based on facts.”

She suggested abstaining from a decision until the council’s Oct. 15 meeting.

At previous meetings, city staff have discussed buying enough machines to go forward with the sewer districts as scheduled, meaning the city would need at least one per district — as two districts are usually under construction concurrently each year.

Miller said the city has not gotten that far in the decision-making process yet, and is trying to focus now on whether the treatment system will be the fix the city is looking for.

“We’re gonna test this and see how much we have left with the project, then look at leasing more units,” Miller said. “There’s a lot of thought still to go into doing a full district (under this system).”

The system will actually be a composite of two units pieced together, Miller said.

The primary unit will consist of a tank, which will be regulated to handle the flow of water coming out of the ground.

“All of the gas and water that comes out of the hose into the swale now would come into the tank,” Miller said. “We’ll connect it with piping to a two-stage treatment process.”

The first stage will separate the gas from the water, and is a standard piece of “odor control equipment,” Miller said.

That unit is designed to remove 99 percent of the gas and odor.

The second stage brings the hydrogen sulfide into contact with an agent that is supposed to neutralize the gas.

“It’s an iron oxide treatment unit, which is a media that causes a reaction between the iron oxide and the H2S and makes it inert,” Miller said.

The second stage, he said, removes 99 percent of the gas in the remaining water, essentially reducing the hydrogen sulfide to .1 percent of concentration it had when it entered the unit.

From there the water would flow into the swales, as the city is permitted to do by the Florida Department of Environmental Protection.

“This is standard in the wastewater industry,” Miller said. “It’s usually used for lift stations where odor is a problem. In this case the water would just come out of the ground.”