CINCINNATI -- The million-gallon oil spill that fouled two rivers and cut off public water supplies in three states is thinning and should dissipate well before it reaches the Mississippi River, an Ohio River agency said.

"It's going to dissipate and dilute itself out. That's what we're seeing," said Jeanne Ison, spokeswoman for the Ohio River Valley Water Sanitation Commission, which monitors the river's water quality.

"We do not believe measurable quantities will be detected by the time it gets to Huntington," W.Va., said Tom Voltaggio, chairman of an Environmental Protection Agency response team from Philadelphia. It is expected to reach Huntington in two weeks.

The commission, made up of representatives of Ohio Valley states and the federal government, estimated that at current speeds the slick will arrive Feb. 5 in Cincinnati; Feb. 12 at Louisville; Feb. 15 at Cannelton, Ind.; Feb. 17 at Evansville, Ind., and Feb. 24 at Joppa, Ill.

The next town to be hit is Sistersville, W.Va.

Ice and cold weather have slowed the slick's speed to one-half mile per hour.

An Ashland Oil Co. storage tank collapsed near Pittsburgh on Jan. 2, pouring the oil into the Monongahela River, which flows into the Ohio. The slick, now about 50 miles long, has interrupted water service for hundreds of thousands of people in Pennsylvania, Ohio and West Virginia as it floats down river.