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March 6, 2012

EAU CLAIRE - With the rapid expansion of frac-sand mining in Wisconsin there has been a corresponding increase in soil-exploration drilling as landowners and others seek to identify large sand deposits.

The resulting bore holes, unless properly sealed, present a risk to groundwater resources because they create a pathway for surface runoff to contaminate underground aquifers.

Groundwater experts with the state Department of Natural Resources are reminding individuals involved in these drilling operations that state law requires the proper abandonment of all boreholes or drill holes exceeding 10 feet in depth or which intersect groundwater. Drillers are required to file a report upon abandonment.

"These rules are in place to protect precious public water resources that are of inestimable value," said Michael Blodgett, DNR's drinking water and groundwater program manager for west central Wisconsin. "Professional well drillers are fully aware of these requirements, but we are asking all drill operators to become familiar with the rules and to follow both the spirit and letter of the law."

Blodgett notes landowners would be smart to make sure drillers properly close boreholes on the land.

The rules for properly abandoning a drill hole are established in NR 141.25, Wisconsin Administrative Code. Leaving holes open can create a direct conduit for entry of contaminants to waters of the state and is a violation of chapter 281, Wisconsin Statutes.

State law defines a borehole as "a circular hole deeper than it is wide, constructed in earth material for the purpose of either installing a well or obtaining geologic or groundwater related data." Boreholes are also referred to as drillholes.

NR 141 addresses sealing requirements for boreholes and groundwater monitoring wells. It states, among other requirements, that "boreholes and groundwater monitoring wells shall be abandoned by complete filling with neat cement grout, bentonite-cement grout, sand-cement grout, concrete or bentonite-sand slurry."

While the code specifies that a bore hole be properly abandoned within three days of its use being discontinued, DNR encourages drillers to close exploration boreholes immediately to avoid the potential for soils collapse and bridging to occur in the hole.

See silica (frac) sand mining for information on NR 141.25 along with a form to be submitted to the local DNR office after abandonment.

FOR MORE INFORMATION CONTACT: Michael Blodgett, DNR drinking water and groundwater program manager for west central Wisconsin, 715-839-3745, Ed Culhane, DNR communications, 715-781-1683.

Last Revised: Tuesday, March 06, 2012

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