DEQ Says Sewer Not To Blame
Cedarville Bay Weed Growth
By Paul Gingras

In the struggle to cleanse Cedarville Bay of excessive weed growth that has reduced boater traffic and damaged the local economy, citizen groups suggest that sewage treatment discharge into the bay is nurturing plants and must be redirected. The Department of Environmental Quality (DEQ), however, says it is natural conditions in the bay that have exacerbated the growth of an invasive aquatic plant, and the sewage treatment system is fine.

These natural factors, not lagoon effluent, are the cause of the problem, said district geologist Randy Conroy of the DEQ Water Bureau.

A proposal by residents to redirect the discharge into a wetland may provide a temporary benefit, but eventually would result in a pass-through of nutrients to the bay, Mr. Conroy said. The DEQ does not allow treated wastewater discharges to stagnant waters such as wetlands. Further, he said, the current levels of phosphorous from the sewage treatment discharge does not warrant additional removal to protect the bay.

Mr. Conroy inspects the sewer system regularly to ensure that it meets standards set by the Environmental Protection Agency. He has inspected the sewer system in Clark Township twice since April.

If there were significant amounts of phosphates in the sewer water, it would nourish the weeds, however, phosphates in the township's sewer lagoons are treated with ferrous chloride, and water discharge meets federal standards, he said.

Phosphates are chemicals common in dishwashing detergents and human sewage.

Municipalities that fail DEQ water quality standards are subject to daily fines of $27,500, he added.

"As far as our programs go, the discharge lagoons [at Clark Township] attain higher discharge quality for phosphorous content than any other stabilization lagoons in the Upper Peninsula," he said.

Phosphate-reducing ferrous chloride is pumped through the public sewer system, and hundreds of gallons are added to the treatment lagoons, he said. Once treated, the discharge runs into Pearson Creek and makes its way into Cedarville Bay.

Mr. Conroy blames natural sediment depositing conditions that help swift-growing Eurasian watermilfoil for the problem. This deposit condition isn't new; the land survey of 1857 noted the presence of muck in Cedarville Bay, he pointed out.

Eurasian watermilfoil is an invasive aquatic plant growing throughout the Les Cheneaux Islands area, including Cedarville Bay.

"Predominantly, conditions were available for it to take root," Mr. Conroy told The St. Ignace News.

Milfoil's domination of Cedarville Bay is the result of quiet waters that do not mix swiftly with deeper Lake Huron waters, nourishment from organic material carried to the bay by runoff, and low water levels that have made it possible for more sunlight to reach the plants, he said.

He also speculated that higher water temperatures, possibly resulting from global warming, may be contributing to conditions that make the plants thrive.

In addition to the Eurasian species, the native northern watermilfoil is another problem plant for waterways, he added, but if there were a phosphate problem in Cedarville, that plant would be found in the sewage treatment lagoons, like it has at lagoons elsewhere.

"I don't believe there is excessive water flora . . . in [Cedarville's] wastewater," he said.

Citizens groups who seek to eliminate the weeds cite a 1990 sewer expansion as a cause for a phosphate increase in Cedarville Bay. It was around this time that plants flourished, they point out.

The project included a shift from groundwater discharge to Pearson Creek, Mr. Conroy said, adding that the DEQ originally approved the discharge to land, not water. The pre-1990 sewage system did not include ferrous chloride addition and probably discharged more phosphorous to the bay than the current system, he said.

Eurasian watermilfoil poses a difficult problem that is insufficiently understood and is being studied in Wisconsin, Mr. Conroy said.

At Les Cheneaux, people have attacked its growth with weevils that eat the plant, and have cut it down with mechanical harvesters, but the problem persists.

To fight the spread of the plant, Mr. Conroy said it is critical to clean boats. A plan to dredge area waterways would remove much of the weeds and clear the waterway, however, he added, Eurasian watermilfoil is thought to take root from the broken parts of disturbed plants, each of which can settle elsewhere and start new plants.