The unprecedented blue-green algae bloom seen last October in Candlewood Lake may be a sign of worse things to come.

In its wake, an environmental consultant was hired by the five towns surrounding the lake -- New Milford, Sherman, Brookfield, Danbury and New Fairfield -- to study water quality issues.

The consultant has concluded remedying the primary cause of the bloom would likely be prohibitive.

"The watershed is having a small affect in the nutrients overload," said Mark June-Wells, of New England Environmental, "but the most serious cause is coming from the lack of oxygen in the lake's deep center."

Runoff into the lake from the watershed puts nitrogen, phosphorous, salt and other pollutants -- referred to as nutrients -- into the lake's water, polluting the water quality.

The depletion of oxygen in the deep center of the lake causes massive phosphorous releases from the lake bed soil, he explained.

"We're always concerned about the water quality," said Larry Marsicano, executive director of the Candlewood Lake Authority. "Fortunately, Candlewood has an amazing resilience, given the development of its watershed."

"But that resilience won't last forever," he added. "We have to get a handle on the nutrients coming from the watershed."

Managing the deep lake center phosphorous releases would be "a massive undertaking," June-Wells said.

"It would require the cooperation of the five towns, the CLA, and (owner) FirstLight utility company," he remarked. "The cost could be prohibitive."

He said there woulod be two ways to manage the phosphorous releases.

1) Aluminum sulfate could be released into the water to decativate the phosphorous by capping the soils.

2) Mixing could be done either through aeration or by installing a circulation system.

To accomplish aeration, air would be injected directly into the bottom of the lake. A circulation system would create a current in the water, June-Wells explained.

"Using any of these solutions would be a massive undertaking," he cautioned.

June-Wells' six-month study of the lake confirmed what a CLA study had previously found.

The CLA study analyzed water quality data gathered by the authority from 1985 to 2012 to determine if there had been an outstanding trend. By and large, Marsicano said, they couldn't.

"Starting in the 1950s, water quality in the lake started to decline," Marsicano said. "As the watershed became more highly developed, the decline in water quality continued into late 1970s and early 1980s."

"Then research started on issues surrounding Candlewood," he added, "and since the early 1980s, what we've seen is fluctuation in the water quality."

Three of the five towns on the lake --New Milford, Brookfield and New Fairfield -- have taken action to reduce nutrient pollution by adding requirements to their zoning regulations calling for site planning.

How much impervious surface a finished site would have would be determined. A system would also be needed to treat storm water runoff from nearby impervious surfaces.

"We've talked about sewering sections of the lake perimeter, but that would not be cheap," Marsicano said. "In the worse-case scenario, algae blooms would be more frequent, forcing the beaches on the lake to be closed. Blue-green algae also produces toxins."

The mayors and first selectmen of the five towns plan to meet with the CLA, Marsicano said.

stuz@newstimes.com; 860-355-7322