to cleanse St. Clair River
will remove tons of chemicals in sediment
Gene Schabath / The Detroit News
ST. CLAIR SHORES
-- Environmentalists hope voluntary dredging by Dow
to remove tons of mercury and chemical-laden sediment from
the St. Clair River will inspire other companies along the
waterway to do the same.
Beginning May 1, Dow Chemical of Canada
will use a hydraulic dredge to suck up sediment that has
been on the river bottom for as long as a half-century.
The sediment is so toxic in some areas
that species of fish and clams, normally tolerant of polluted
water, died after being left in cages in the sediment during
studies in 1996.
The Dow cleanup is a significant breakthrough
for ecologists, such as the Bi-National Public Action Council,
which has been trying for nearly two decades to get the
river cleaned, said Art Ostaszewski, environmental analyst
with the Michigan Department of Environmental Quality.
"The public is cautiously optimistic that
things will finally get cleaned up," he said.
But some Michigan environmentalists are
concerned that sediment residue would be released into the
water column during the dredging. That residue could reach
drinking water intakes downstream both on the Canadian and
Michigan sides of the river, said Doug Martz, chair of the
Macomb Water Quality Board.
The St. Clair River is an international
waterway that separates Michigan from Ontario, Canada. Martz
said there are 13 municipal drinking water plants on the
Michigan side of the St. Clair River and Lake St. Clair.
Tests show the water does cross the river onto the U.S.
side, he added.
"We want drinking water plants on the
American side notified if there is a failure of the hydraulic
dredging system," Martz told members of the Bi-National
Action Plan Council, which is made up of Ontario and Michigan
Severe cases of mercury poisoning can
cause brain damage and death to humans. Exposure to chlorine-based
chemicals such as hexachlorobenzene can cause liver and
kidney problems, arthritis, thyroid tumors and increased
risk of cancer to humans.
Layers of contaminated sediment can be
found over a five-mile stretch of the river bottom, environmentalists
The contamination is the tragic legacy
from chemical and petroleum companies that have done business
for decades in the region of Sarnia, Ontario, known as Chemical
Valley. Most of the contaminants, such as hydrocarbons and
mercury used in the production of chlorine and other chemicals,
were discharged into the river for decades through sewer
"Dow admits it is at fault and now we
are doing something about it," said Catherine Creber, an
environmental expert with the company. "It was contaminants
released from the Dow plants in the 1950s and 1960s. Our
focus has been to stop the discharges, which we have done.
And now we're to remove it."
The dredging project will cost Dow $10
million. The company is expected to remove 28,000 cubic
yards of contaminated sediment in an area directly across
from Marysville in St. Clair County, about a 90-minute drive
The dredging area is 3,000 feet long and
120 feet from the river banks.
Dow said it will use a small, pilot dredging
project in the area to make sure the hydraulic dredge system
is safe. That system operates like a giant vacuum and leaves
little chance for residue to escape into the river.
During a 1996 dredging by Dow of 180 cubic
yards of severely contaminated sediment, residue from the
river bottom was stirred and later detected at the Walpole
Island water intake 20 miles to the south. In that operation,
the sediment was scooped from the river bottom.
Dow will conduct tests for elevated contaminant
levels in the water 300 feet downstream of the dredge site
during the cleanup operation.
Removing mercury and other contaminants
from the river bottom also will impact the health of fish
that live in the river, said Gary Johnson, project coordinator
for Ontario's Ministry of the Environment. Some fish carry
advisories for human consumption because they contain high
levels of mercury and other contaminants.
"The levels of mercury in fish are way
down compared to the 1960s, and this will result in even
lower levels," Johnson said.
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