ORLEANS — Uncle Harvey's sick, and those who care are discussing what to do about it.
The 7.5-acre pond south of Pochet Road has been flagged for harmful algal blooms by the state Department of Environmental Protection, and the state Department of Public Health has issued advisories to avoid contact with the water.
Since the turn of the century, volunteers have been monitoring water quality in Uncle Harvey's and other local ponds. This year, their data were augmented with studies by the Coastal Systems Program of the School for Marine Science and Technology (SMAST) at the University of Massachusetts Dartmouth.
On Monday, the town's marine and fresh water quality committee reviewed a draft management plan for Uncle Harvey's Pond with Ed Eichner and Brian Howes of SMAST. The discussion centered on controlling phosphorus, which encourages algal growth.
“Pretty much for all the ponds on the Cape except in the (National) Seashore, you have driven them to be phosphorus-sensitive because you've added so much nitrogen,” Eichner said. “Just adding a pinch (of phosphorus) adds more growth.”
The watershed of which Uncle Harvey's is a part contributes 29 percent of its phosphorus load, almost all of that from septic systems. Eventual sewering, perhaps with a connection to any such system if built at Meetinghouse Pond, is one solution. Relocation of leaching fields for existing systems might help, too.
With 67 percent of the phosphorus load in-water, the focus shifted to the pros and cons of possible treatments in the pond itself. The draft report looked at aeration, alum application and dredging, and provided cost estimates.
Aeration adds oxygen at the coming together of the pond's water and its sediment level “and stops the chemical release of phosphorus to the water column,” the SMAST draft report states. An alum application binds phosphorus in the sediments to prevent future release, and dredging would remove sediment and attendant phosphorus.
The draft report states that sediment removal from freshwater ponds “does not appear to ever have been used on Cape Cod,” and that securing sites for dewatering and sediment disposal could make permitting difficult. As for aeration, the analysis advises against using direct air flow to introduce oxygen as “the amount of flow would be roughly equivalent to placing 40 leaf blowers on the bottom (of the pond) and may create aesthetic issues for pond users.” Direct oxygen addition would be an alternative.
Alum application “is typically the favored phosphorus inactivation technique in Cape Cod ponds and has seen wide-spread use,” the report states. The treatment, usually a mix of aluminum sulfate and sodium aluminate, has been used 12 times on the Cape, including in Long Pond (Brewster/Harwich) and Lovers Lake/Stillwater Pond (Chatham).
The draft plan recommends that Orleans use “either an alum treatment or aeration as an in-pond treatment to address sediment phosphorus regeneration. The cost differential between these two options is relatively nominal, but they do have differing levels of maintenance/operation costs and long-term commitment. An aeration system would have operation and maintenance costs while an alum preparation, once done, could yield benefits for a decade or more, according to the draft report. “If the alum treatment lasts for 15 years or more,” it states, “the alum treatment would definitely be more cost effective than the aeration system.”
At Monday's meeting, committee members talked about the options. “I'm very impressed with the report, the degree of science and the way it's presented,” said Ed Hafner. “You remarked that community acceptance is a very important piece of the solution. I believe aeration can certainly gain community acceptance: no nasty chemicals, just pumping in air. If it's ineffective, you can always resort to alum treatment later on.”
Lou Morongell, an Uncle Harvey's Pond abutter who could not attend the meeting, asked that his statement be read. Unlike Hafner, he called the draft report “virtually impossible to understand and comment on.” He's opposed to alum use, calling it “a temporary nutrient cap, not a sustainable solution.” He asked the committee for “fair consideration to vetting companies, such as Gaia, who are bringing to market very promising solutions.”
Committee member Betsy Furtney, who sat in the audience because she is an Uncle Harvey's abutter, referred to a recent study of alum in Cape ponds (click here) that she said offers “verified data that talks about the effects of alum and dismisses some of these outdated thoughts.” Alum is an effective and “least cost” method, she said.
Other speakers called for greater citizen notification and involvement in the process. The committee is scheduled to continue the conversation at its next meeting Jan, 22 at 10 a.m.