By Bob Zientara | Barron News-Shield
A recent Chippewa County study of the effects of frac sand mining and agriculture on surface and groundwater was completed with the cooperation of the Barron-based office of Superior Silica Sands.
Sources cited by the company and Wisconsin Public Radio drew varying conclusions about the study data and emphasized different aspects of the study results.
The company contacted the Barron News-Shield during May to draw attention to the report, and the comparisons it makes between the use of subsurface water supplies for agriculture and sand mining.
Sharon Masek, who is responsible for mine planning and industrial relations for the company, said that in 2014, Superior Silica Sands was approached by Chippewa County, state government officials and officials with the U.S. Geological Survey.
The company provided researchers and government officials with access to mining operations in Auburn (township in Chippewa County) and Dallas. Masek said sand mined at both locations is from an identical sandstone formation, which provided similar scientific data for study conclusions and projections.
Masek said one of the purposes of the study was to look for the impact of frac sand mining on available groundwater and compare it to the impact of agriculture.
Presented to a recent meeting of the Chippewa County Board of Supervisors, the study notes that about three billion gallons of water are consumed in the county each year. About 6 percent of that water is used for frac sand mining, while 70 percent is used for agricultural irrigation.
“Of the 3 billion gallons that all of us use (in the county), it amounts to only two percent of the amount of groundwater that’s actually available,” she added. “The bottom line is that (sand mines) are not sucking the water supply dry.”
The study also compares the effects of sand mining and agriculture on in terms of surface water, effects on streamflow and the potential for rain to filter into the groundwater after the land is used for mining and/or agriculture.
The study also models what could happen to streams in areas where frac sand mining or agriculture might occur.
Frac sand mining might cause “the upper reaches of some feeder streams (to) dry up, but (the study also indicates that) there is no impact on wider streams and rivers.”
Masek said the Auburn mine was studied by Holly Dolliver, professor of geology and soil science, and department chair of plant and earth science, at the University of Wisconsin-River Falls. Dolliver and her students studied the effects of mining on the ability of rainwater to filter into the groundwater supply after a mine is reclaimed.
Topsoil from a reclaimed mine needs time to regain characteristics it had before mining began, Masek said
“Within the first year or two, (water infiltration) for mining is very similar to agriculture,” she said. “When you reclaim a mine, you may have pushed the topsoil off five years before you put it back. If it sits in a pile that long, (the topsoil can lose) microbes, and texture. Over time, it regains texture.”
Effects On Streams
In a May 7 online story copyrighted to the University of Wisconsin Board of Regents, the UW-System and the Wisconsin Educational Communications Board, reporter Rich Kremer said the three-year study showed “stream levels can be negatively impacted by frac sand mining and irrigated agriculture,” and that “the results can inform future regulations on high-capacity wells and industrial sand mining operations.”
In addition to the ratios of agriculture (70 percent) and sand mines (6 percent), the study also showed public wells in cities and villages use 22 percent of Chippewa County’s groundwater supply.
“Researchers found that the average amount of groundwater used at five mines within the study area was around 35 million gallons of water per year between 2012 and 2014,” Kremer reported. Computers processed the numbers and projected the impact “if 10 percent to 100 percent of the sandstone deposits were mined.”
Headwater streams near sandstone “bluffs targeted by sand mining companies saw (surface water flow) reductions based on computer modeling,” he added.
The story quotes Mike Parsen, Wisconsin Geological and Natural History Survey, and Paul Juckem, U.S. Geological survey. Parsen said truck activity on mining sites “tends to decrease infiltration (of rainwater into the groundwater supply) due to compaction and just the change of that land-use cover.”
Juckem said that infiltration rates were low on the newly-reclaimed sites of former mines in Taylor County.
“But as the prairies got older and developed deeper and more mature root systems, we found that in those sites the measured infiltration rates were typically higher,” Juckem said in the WPR story.