The Influence of Frac Sand Mining on Soil Fertility and Plant Productivity.

Hydraulic fracturing has increased the demand for high grade silica or “proppant” an important component of injection fluid. This has led to the expansion of sand mining in Wisconsin and Minnesota. We analyzed landscape change between 2006 and 2013 at seventy-eight silica mining operations in Wisconsin. Parcel boundaries were delineated using 2013 aerial imagery from the National Agriculture Imagery Program. Data from the 2006 National Land Cover Database was used to determine land cover within parcels prior to the fracking boom to compare with 2013 land-use. The SSURGO database was used to calculate soil carbon and nitrogen loss. The National Agricultural Statistics Service Cropland Data Layer was used to calculate different crop acreages within each parcel prior to mining. Dollar estimates were calculated from 2006 through 2013 using the Wisconsin Agricultural Statistics Report.

From 2006 to 2013, 1,130 acres of forest and 3,710 acres of cropland were removed to establish mines. We estimate a loss of 130,000 tons of soil carbon (476,710 tons of CO₂) and at least 6,000 tons of soil nitrogen with a total soil fertility value of $22.3-26.7 million dollars (i.e., $6,010-7,197 per acre) across formally cropland parcels. The cumulative value of the four dominant crops is estimated at $7,600,000 or $2,049 dollars per acre in lost revenue or $97,459 per farm. Forest productivity loss includes 381 and 68 thousand tons of aboveground and soil carbon, respectively, with current stumpage value of $176,226-275,435. Forest soil nitrogen loss amounts to 145 tons with an equivalent fertility value of $74,609-174,524 (i.e., $66-154 per acre per year).

As shale demand for silica increases by 80+ tons per lateral per quarter the role of reclamation will become more acute in the Driftless region of Minnesota and Wisconsin with studies like this integral to holistic reclamation  policy and success metrics.