SITE INFORMATION AND CORRESPONDENCE

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Mr. Stewart Black - 2 - 28 February 2017 ❑ In December 2005, fertilizer operations ceased at this facility. ❑ In 2005, 2006, 2008, and 2010 site assessments, including soil and grab groundwater sampling, were conducted . ❑ In 2008, groundwater monitoring wells were installed. ❑ In 2011, soil was excavated to depths between 3 feet and the water table, which was about 7.5 feet bgs. The excavation removed about 10,800 tons of soil containing nitrate, ammonium, and sulfate. The soil was disposed of at a licensed facility, and the excava- tions backfilled with clean soil. ❑ In 2016, sampling showed groundwater concentrations of nitrogen,were decreasing, but sulfate remained fairly constant. Arsenic and vanadium have also been identified in groundwater above water quality objectives, but as explained below, these constituents are probably naturally occuring and not related to site activities. Their concentrations are also decreasing post-excavation. Issues Nitrogen in soil. The cleanup goal for nitrogen (the sum of nitrate-n plus ammonium) in soil is 100 mg/kg. From the 76 confirmation samples obtained following the November 2011 soil excavation, four samples contained between 100 and 150 mg/kg nitrogen, slightly exceeding the clean- up goal. Only 2 of the 76 samples contained significant amounts of nitrogen, 432 mg/kg and 537 mg/kg nitrogen, respectivley. Therefore, Deere & Company has removed most of the soil pollutants from the former Lesco site. Nitrate and sulfate in groundwater Nitrate in MW-4, nearest the excavation, decreased from 200 mg/L in 2013 to 10.8 mg/L in 2016, which is slightly above the water quality objective of 10 mg/L. Ammonium decreased from 367 mg/L in 2013 to below detection limits in 2016. In MW-3, downgradient of the ex- cavation, nitrate declined from 143 mg/L in 2012 to about 66 mg/L in 2016. While this is above the water quality objective, the concentrations are on a declining trend and are ex- pected to meet the water quality objective of 10mg/L in 2021. These trends are illustrated in Figure 2a. A source of sulfate exists on the adjacent property to the east, where groundwater concen- trations are about 1,000 mg/L. In monitoring wells on the Lesco site, sulfate concentrations in MW-4, about 100 feet from the sulfate facility, were 900 mg/L in 2016, and have varied between 750 m/L and 1,600 mg/L since monitoring began in 2008. Sulfate in MW-3, about 500 feet from the sulfate facility, has been consistent between 200 and 265 mg/L since 2008. Sulfate concentration trends are shown in Figure 2b. Arsenic and Vanadium Arsenic in monitoring well MW-4 decreased from 400 ug/L in 2013 to 142 mg/L in 2016, which exceeds the water quality objective of 10 ug/L. This well also contains vanadium which decreased from 167 ug/L in 2013 to 115 ug/L in 2016, as shown in Figure 2a. This concentration is above the public drinking water notification level of 50 ug/L, but below 500 ug/L, the level at which a public water supply would be advised to remove the water from public service.