Quantifying Heavy Metals in Subsurface Waters of Frac Sand Mine Reclamation Areas.

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.  A 3-acre reclamation site was established in 2015 to quantify trace metals in subsurface waters.  Plots were established 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, on average 32 cm.  Subsurface water quality was monitored using suction cup lysimeters installed at a 45 cm depth at 5 locations within each plot. Leachate samples were collected bimonthly during the growing season and analyzed for heavy metals using ICP-MS.  The results from our field season will be presented.