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EWS
Slimy, stinky algae in Honeoye Lake
Chemical treatment could subdue it for a decade
Misty Edgecomb
Staff writer
(August 3, 2006) — A few years ago, Honeoye Lake was so clogged with
decaying algae that local residents planning a picnic on the lakeshore
couldn't bear to get out of their cars.
"It looked like pea soup and the stench was just horrific," recalled
Bonnie Drake, town supervisor in Canadice, on the lake's west side.
This summer, the annual bloom caused by sustained warm weather is just
beginning, but local residents have no doubt that the slimy mess will
return.
So the small Ontario County towns of Canadice and Richmond have raised
nearly $160,000 to address the algae problem, using the same strategy that
has been considered a success in Irondequoit Bay.
This fall, the lake will receive a one-time treatment of aluminum sulfate,
or alum, in hopes of containing for about a decade the excess nutrients
that feed the summer algae.
"All the stakeholders think that this is the right way to go," said Terry
Gronwell of Canadice, president of the Honeoye Valley Association.
Originally, the alum treatment was slated to be completed by early summer.
But the special barge that the contractor uses to apply the alum had
engine problems, so the application has been delayed until at least
September.
Known as the most nutrient-rich, or eutrophic, of the Finger Lakes,
Honeoye's floor is covered with centuries of phosphorus-rich sediment,
which has been building up since the Finger Lakes were formed at the end
of the last ice age about 11,000 years ago.
"The sediments are very rich and very deep," said Thomas Harvey of the
Ontario County Planning Department, which approved the permits for the
alum treatment.The lake bottom contains not only sediments from decades
ago, when shoreline residents discharged their sewage directly into the
lake, but also from centuries of natural erosion. High amounts of
phosphorus can result in growths of weeds and algae, which clog the lake
and make swimming and boating unpleasant, Harvey explained.
The lake has struggled with algae and weed problems for years. The
construction of better sewer systems for shoreline residents has brought
some improvement. However, the introduction of such invasive weeds as
Eurasian watermilfoil and curly-leaved pondweed that die off each fall has
loaded the lake with nutrients.
The presence of zebra mussels, which were discovered in the lake in 1998,
has worsened conditions because the clearer water created by the
filter-feeding shellfish allows more sunlight to reach algae and weeds.
A phosphorus 'block'
A natural nutrient, phosphorus comes from a variety of sources: dead
plants and animals decaying on the lake bottom, runoff from shore
properties like lawns and farmland, and from stored phosphorus within the
sediment itself. In Honeoye, the sediment is the biggest problem,
constituting 43 percent of the phosphorus released into the water each
year, according to a recent study.
Each summer, the shallow lake becomes oxygen deficient, which causes
phosphorus to leach out from the sediment and into the water.
Aluminum sulfate solves this problem by binding with phosphorus, trapping
it at the lake bottom.
The strategy has been used across the nation since the early 1980s with
few complications. In fact, alum treatment is often used to clarify public
drinking water and swimming pools.
"It's a pretty standard kind of thing," said Mark Noll, an assistant
professor of geochemistry at State University College at Brockport.
The primary environmental concern is the possibility that too much
aluminum sulfate can poison fish or cause the water to become unhealthily
acidic.
Some local fishermen have raised concerns that alum treatments proposed
for the Finger Lakes region could harm fishing.
But state environmental regulators are confident that the Honeoye
application will be safe — with the right dosage and ongoing testing by
state environmental officials, said Sean Hanna, regional director for the
Department of Environmental Conservation. And although sometimes alum can
cause lakes to become acidic, Honeoye's chemistry should offer some
measure of protection.
"You can do the analysis in the lab to determine the dosage to be added.
That's a pretty reasonable approach," said Joseph Makarewicz, a professor
of biology and environmental science at the SUNY Brockport.
"And fish usually just get out of the way," he said.
Other options weighed
The Honeoye Valley Association has already addressed agricultural runoff
problems and educated homeowners about lake-friendly lawn care, but an
internal strategy was necessary, Gronwell said.
Over several years of study, the association considered several options,
including aerating the sediment to keep it filled with oxygen. Aerating
would initially cost about $200,000 with at least $15,000 in annual
electricity costs; for comparable benefits, the strategy couldn't compete
with alum treatment.
Dredging, too, was impractical. Removing the phosphorus-laden soil could
disrupt the lake's ecology, and possibly create new environmental
problems.
"We've got to be concerned with that last 200 years of sediment and what's
in it, whether it's toxic," Harvey said.
Besides, dredging such a large area would be "outrageously expensive" at
more than $35 million, according to the project's environmental impact
statement.
The alum treatment will be done sometime between Sept. 15 and Oct. 31.
About 120,000 gallons of aluminum sulfate will be applied at between 6 and
10 feet beneath the lake's surface in all areas of the lake deeper than 18
feet.
At about $160,000, the alum treatment isn't cheap, but the towns of
Richmond and Canadice have included the funds in their municipal budgets
in hopes of solving the problem. Once completed, the alum blanket should
control phosphorus levels, and as a result, algae blooms, for seven to 10
years, Gronwell said.
"The alum eventually breaks down or gets covered up by other sediment,"
Makarewicz said.
An imperfect solution
In Irondequoit Bay, where alum was applied as a pilot project in 1982 and
over half the bay floor in 1986, phosphorus release initially decreased by
more than 90 percent. But the treatment began losing effectiveness by
2000. The county has aerated in recent years and is studying how to
address the problem in the future.
Though it would likely be effective, the county lacks the funds — well
over a million dollars — that would be required to repeat the alum
treatment, according to Charlie Knauf, an environmental health project
analyst at the Monroe County Health Department.
Conesus Lake has been considering alum treatment for several years as
well, but controversy among fishermen and the $1.3 million price tag have
stalled discussion. Sodus Bay, about 40 miles east of Rochester, was set
to pursue a project this summer but encountered trouble with state
environmental permits and has abandoned the idea for now.
"It's not a one-shot cure-all," Noll said.
At Honeoye, as well, problems remain. The milfoil that snags swimmers'
legs won't be affected by the alum treatment. In fact, reducing algae
growth has, in some lakes, boosted weed growth.
"We fully expect that (alum) will solve the algae problem, but it doesn't
do anything for the weeds," said Richmond Supervisor Randy Pawley.
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