State geologist: Frac sand mine small threat to water supply

DECORAH — The porous bedrock of northeast Iowa, known as karst topography, does not pose a great obstacle to the mining of frac sand, State Geologist Bob Libra told the Winneshiek County supervisors on Monday.

'When people hear 'karst' in northeast Iowa, they think of increased risk of groundwater and stream pollution, but the prime frac sand deposits in Winneshiek County are not especially vulnerable,' Libra said.

The underground stratum prone to sinkholes, tubes and caves, he said, is Galena limestone, which is not present in the northeast portions of the county with the coveted deposits of St. Peter sandstone.

Libra said a sand processing facility, in which the impurities are washed from the silica sand, likely would pose a greater threat to water quality and quantity than sand mines.

'If you just come in and dig sand out, there is very little risk to the water,' he said.

Libra said a single frac sand mine would pose no more threat to the environment than a gravel quarry or standard sand pit.

But in southeast Minnesota and southwest Wisconsin, where frac sand mining is big business, dozens of mines have been rapidly established in confined areas, compounding the risks, he said.

Supervisor Dean Thompson said the supervisors invited Libra to speak as part of an information-gathering process that could lead to modifications of the county's zoning ordinance.

Earlier this year, the supervisors extended through October their moratorium on frac sand mining in the county to buy time for additional study.

In neighboring Allamakee County, the supervisors, after enacting a similar moratorium, approved an ordinance that severely restricts where frac sand can be mined in the county.

Allamakee County Planning and Zoning Commissioner Thomas Blake said Monday that the county has received no mining applications since the ordinance was approved last June.

Opponents of frac sand mining have cited several concerns that include not only water quality and quantity impairments but also human health threats, road damage, traffic safety hazards and destruction of scenic bluff landscapes.

Iowa has just one frac sand mine, operated by Pattison Sand Co. near the town of Clayton in Clayton County.

The round, crush-resistant quartz particles are in demand for hydraulic fracturing, the process by which water, silica sand and chemicals are injected under high pressure into underground shale deposits to release otherwise inaccessible oil and natural gas.

With shale gas now making up 25 percent of U.S. production, Libra said demand for frac sand likely will remain strong for the foreseeable future.