Ohio bedrock is expressway for pollution

GIBSONBURG, Ohio (AP) — Late last month, state scientists gathered in a gravel parking lot in this small northern Ohio village and poured a small amount of dye into a 30-foot well. Then they waited.

“I think it’s going to take a couple hours at the earliest,” said Heather Raymond, a hydrogeologist with the Ohio Environmental Protection Agency.

In fact, it took more than a day before the dye was detected in three of the village’s drinking-water wells.

The time it took to reach the water supplies will give valuable clues about its labyrinthine path.

Gibsonburg has one of 167 public water systems in Ohio where an ancient, cracked layer of bedrock called karst lurks a few feet below the soil. Those cracks, formed over millions of years, can become an expressway for pollution.

Some of the larger communities underlain with karst include Findlay in Hancock County and Dayton suburbs such as Clayton, Huber Heights and Trotwood.

“In a sand-and-gravel aquifer, it might take five years for a contaminant to travel a mile,” said Raymond. “In a karst area, it might take five days.”

The results from this and three other dye tests the state has performed since 2007 will help officials tailor plans to protect people from toxic spills and diseases that can contaminate drinking water.

“In an emergency, we would have to respond more quickly,” Raymond said.

Karst is a term used to describe layers of limestone and dolomite that formed in the western half of Ohio up to 440 million years ago.

Water from rains and streams slowly eroded the rock, widening tiny natural fractures into larger cracks and even caves.

People who get their water from karst aquifers are at greater risk after toxic spills at nearby factories, overturned tanker trucks and derailed trains.

However, most of the contamination results from failing septic tanks, said Heather Lauer, an Ohio EPA spokeswoman.