Quantifying the Effects of Frac Sand Waste Fines on Subsurface Water Quality.

Silica sand mining for frac sand production has increased substantially in the United States over the last five years. Since only a certain size range of sand is desirable for fracking operations, the processing of sand generates large volumes of waste material, which consists mostly of silt and clay. 'Waste fines' are typically incorporated with overburden and used to fill in the mined area during reclamation. A long-term field study is being conducted in Chippewa County, Wisconsin to evaluate the effects of using waste fines as a soil amendment during reclamation. Frac sand mines are generally located on sandy, shallow soils. While the waste fines have the ability to improve moisture retention and soil physical properties, they are known to contain heavy metals and nutrients that could pose environmental concerns. A 3-acre reclamation site was established in 2015 using a randomized complete block design in a split-plot arrangement with application of waste fines as the main treatment. Waste fines were applied as a 30 cm layer below the subsoil and topsoil. Total thickness of soil layers was an average of 32 cm. For this particular study, subsurface water quality was monitored using suction cup lysimeters. Leachate samples were collected bimonthly during the growing season and analyzed for heavy metals using ICP-MS. The results from our first field season will be presented.