Baltimore officials aren't taking any chances on keeping a thumbnail-sized mollusk at bay.
Worried by the spread of zebra mussels, the fast-breeding bivalves that have infested the Great Lakes, the city is preparing to spend from $2 million to $6 million to protect its public water supply.
The Board of Estimates approved hiring a consulting firm yesterday to complete plans to prevent the black-and-white striped mollusk from clogging water intakes at three reservoirs and 67 miles of water tunnels leading to filtration plants.
Even though no zebra mussels have been found in Maryland, the city "decided to take a proactive approach after seeing what happened in the Great Lakes," said David Scott, chief of Baltimore's water facilities engineering section.
KCI Technologies Inc. of Towson was awarded a $550,000 contract to design chlorine- and heat-treatment systems to kill zebra mussels before they invade intake pipes at the Susquehanna River, and Liberty, Loch Raven and Prettyboy reservoirs.
The firm will spend the next six months finishing preliminary plans begun more than a year ago by Akers International, said George G. Balog, director of public works. The previous company, which received a $750,000 contract to study the potential risk, told the city it would cost $6 million to prevent zebra mussels from disrupting water supplies. But KCI believes the treatment equipment could be installed for closer to $2 million, Mr. Balog said.
"These are incredibly tenacious creatures," said Thomas Hintz, executive vice president of KCI's environmental division. A chlorine-treatment system is being designed for the intakes at the Susquehanna, and Liberty and Loch Raven reservoirs, he said. At Prettyboy, heat will be used to kill zebra mussels instead of chlorine because the water flows from the dam into Gunpowder Falls, a favorite trout stream.
Zebra mussels have created havoc in the Great Lakes since being inadvertently released in 1986 or 1987 by a ship discharging ballast water obtained in Europe. The pesky mollusks carpeted boats, piers and waterworks, causing millions of dollars in damage. Monroe, Mich., found itself without drinking water for 56 hours in December 1989 after piles of zebra mussels and ice clogged a pipeline from Lake Erie.
None of the mollusks has been found yet in Maryland, Mr. Scott said, but larvae were discovered in the upper reaches of the Susquehanna. Fearing anglers might bring zebra mussels into the reservoirs, the city imposed a boating moratorium last year. But after an outcry from sportsmen and recreational boaters, public works officials decided the spread of the mussels could be controlled through boating permits and the planned treatment system.
In the Chesapeake Bay, the salt levels are expected to be too high for the zebra mussel to survive south of Harford County and below Quantico, Va.