May 30, 1999
Sinkholes present problems for well drillers
By Carol Bogart
Staff Writer
People living in Seneca County's Thompson Township are well aware sinkholes there present special problems for well drillers.
Ohio EPA hydrogeologist Heather Raymond says well logs reveal instances of underground caverns where drill stems have fallen three feet or more. Such fractures in bedrock limestone are called "karst" features.
Jack Kramer of Heidelberg's water quality lab says such features may become "solution channels": tube-like conduits for contaminants.
Karst regions, according to the Ohio Department of Natural Resources, "are the most vulnerable natural settings for ground-water contamination." Raymond explains that such fractures and caves have no ability to partially cleanse groundwater of contaminants as a sand and gravel aquifer might.
Instead, she says, contaminated groundwater "flies" through such channels at a rate of 400 to 500 feet per day.
Raymond says the typical speed (or conductivity) in non-karst geology is just one foot per day.
In Seneca County, ODNR has identified various areas with karst features in the limestone (see map) and study of the features continues. Kristin Woodall, with WSOS's Rural Community Assistance Program in Sandusky County, moderated a program last week in Bellevue for potential "stakeholders" &emdash; people who might be able to help assess threats to source water by mapping both sinkholes and potential polluters.
Several counties in addition to Seneca were represented at the meeting. Stakeholders from Seneca County included Scott Rabun from the Seneca County Health District, Jim Raab from the Ohio Department of Natural Resources, who said, "I've done a lot of work in Thompson Township," and Tom Fishbaugh, the new village administrator in Republic.
Ohio EPA says the karst area affecting Seneca County extends from the northeast corner, down through Thompson, Scipio, Eden and Bloom townships. Villages clearly included in the area are Republic and Bloomville. Ohio EPA's Brian Gare says boundaries may widen as public water systems are more accurately pinpointed and additional geological research is done.
To comply with federal regulations under the Safe Drinking Water Act, WSOS's Rural Community Assistance Program's Kristin Woodall says, "What we plan to do is inventory for potential contaminants out there and come up with a management plan." The community, she says, will be asked to contribute to and implement the program.
Patrick Heider, a hydrogeologist with the Bowling Green office of Ohio EPA says, "You don't want to wait until your groundwater is impacted. It's very expensive to clean up groundwater. It's a lot easier to be proactive and not have it impacted by pollution."
Glossary
"Karst" &emdash; A karst is defined by Websters Third New International Dictionary as "a limestone region marked by sinks (sinkholes), abrupt ridges, irregular protuberant rocks, caverns and underground streams."