ORLEANS — The marine and fresh water quality task force heard from the public Feb. 6 on its recommendation that polluted Uncle Harvey's Pond be treated with a mix of aluminum salts to reduce the negative effects of phosphorus there.

“This has been a very careful process,” a woman in the audience told the committee. “Not everyone will like your conclusion, (but) it's more dangerous not to do anything... I'd like us to proceed without fear.”

“Alum is not the same thing as aluminum,” said committee member Carol Etzold. “We're not dumping pure aluminum in any form... It's similar to sodium, (and) sodium is half of every salt molecule. It does not have the same chemical reaction as pure sodium.”

Pond abutter Lou Morongell urged caution. “Once you put it (alum) in there, we're stuck with it,” he said, “short of dredging it out. With all the newer technologies on the horizon or already here, we waited this long, why can't we evaluate some of those that show promise and give them a chance, even on a test basis? We don't know what the long-range repercussions may be 20, 30, 40 years from now of putting this into the pond.”

Ed Eichner, the UMass Dartmouth School for Marine Science and Technology scientist who conducted the study, countered that “alum has been an application for 40 years” in management of lakes. Earlier in the meeting, he discussed an alternative that has drawn interest from some in Orleans: aeration with microbubbles.

“Bacterial addition has not been done in New England,” Eichner said. “There are no quantitative or ecological studies to assess the impact of bacterial addition. It's generally been done in artificial basins: golf course ponds, stormwater retention ponds... It's largely experimental. If it's something the town wants to pursue... you need to understand its impacts ecologically throughout the whole food chain.”

Kevin Galligan, president of the Orleans Conservation Trust, noted that Uncle Harvey's abuts OCT land. “There will probably be inquires,” he said, “if there is any influence of alum that might come onto the property. We have to preserve its natural state.”

“I think you're at the other end of the pond from the part we're going to treat,” said Carolyn Kennedy, the committee's chair.

“Alum treatment would be in the deeper portion of the pond,” Eichner added. “It's typically done with GPS (so the area is) actually constrained. (We) try to do them on days when there's not turbulence. Hopefully, it'll just settle down and there shouldn't be any out along the border in any way.”

Walter North, a member of the conservation commission, asked about examples of alum treatment next to conservation land. Eichner cited Cliff Pond in Brewster, and Kennedy recalled watching Herring Pond in Eastham being treated a couple of years ago. “They do it in sections,” she said. “They set out buoys where they wanted the alum to go... The first day was too windy, then there was a torrential storm, so they bagged it for that period. The conditions have to be right; there's not somebody in a rowboat going out (and tossing it over a shoulder).”

In voting to recommend the alum treatment, the committee cited lower costs than aeration or dredging as well the expectation of better performance and lower maintenance than aeration. The estimated cost for an alum treatment of the pond is $21,211, not including permitting and monitoring expenses.

The next steps in the effort to improve the health of Uncle Harvey's include contacts with each of the direct abutters, approval by the conservation commission, and review by legal counsel.