MUSSELING INLAND

The Journal Sentinel staff

The zebra mussel invasion of Milwaukee has made it as far inland as the Municipal Building on N. Broadway, a full two blocks east of the Milwaukee River.

Already this year, thousands of the striped mussels from river water repeatedly have blocked portions of the cooling system used by that building and City Hall, said Stuart Thompson, mechanical maintenance supervisor for the Milwaukee Department of Public Works.

Costs of labor needed to remove the barnacle-like mollusks have tripled compared with past years, Thompson said Friday. Workers must poke the pests out of narrow tubes in cooling system cylinders, known as chillers. It used to take eight hours to clean and inspect each of the four chillers. Now workers are poking away for 24 hours or longer, he said.

Cleanings will become more frequent, too, from twice a year in the past to four or more times this year.

As river water flows through the tubes, it cools refrigerant chemicals inside the cylinders. Those compounds, in turn, are Leg 1 ends here used to cool a separate water system flowing to offices in the the city government structures. The river water is drained into sewers and treated at the Jones Island plant.

Thompson cannot get rid of the mussels so easily, however. His workers are storing the pests in 55-gallon drums for future disposal. They cannot be shipped to a landfill because federal officials consider them to be hazardous waste.

Why? The mussels filter about one quart of water each day and remove most of the toxic metals and chemicals in the water.

Last year for the first time, city workers found zebra mussels in the cooling system's pumping station, located on the river bank beneath the Kilbourn St. bridge.

One of the pipes coming into the basement of the Municipal Building became so clogged with the mussels earlier this year that workers could not use a valve to shut it off, Thompson said.

City officials are considering several measures to thwart the invasion, said Steve Hiniker, en Leg 2 ends here vironmental policy coordinator for the city Department of Public Works.

One of those options would require flushing the water pipes and chillers with a chlorine solution or other chemicals. Such a step would require the installation of a special system to remove the chlorine before the water could be discharged to the river through a new storm sewer.

Another option is the construction of a cooling tower. Clean water in the tower would be cooled and substituted for the mussel-laden river water.

But The Milwaukee Center and several other downtown buildings also draw water from the river for their cooling systems and they also are experiencing problems with zebra mussels. One possible solution for all those structures would be a so-called district cooling system proposed by the Wisconsin Electric Power Co.

Since the turn of the century, WEPCO has heated nearly 500 downtown buildings with steam from its power plant in the Menomonee Valley. A cooling district would operate in a similar Leg 3 ends here way, with the utility providing cold water for the building chillers of its customers, Hiniker said.

A zebra mussel can grow up to two inches long. It is known for its D-shaped shell with dark and light stripes that vary in color from brown to black and white to yellow.

It forms colonies that block water intake pipes and encrust boat hulls and docks.

The zebra mussel is a native of the Caspian Sea between Asia and Europe, and was discovered in 1988 in Lake St. Clair near Detroit. The mussels likely arrived there in a load of ballast water discharged from a European freighter.

Since that time, the prolific mollusk has spread throughout the Great Lakes and Mississippi River, as well as to inland lakes in Wisconsin and 17 other states. Its invasion of Lake Michigan cost several municipal water systems and power plants more than $5 million from 1990 to 1993.

That amount is expected to double for those facilities by next year.

Copyright 1995
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