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` Ms. Wendy L. Cohen, Chief - 4 -4 ' rr 5 March 2003 present above 1,000 mg/kg at six feet bgs,the maximum depth of samples. Ammonium is also present at concentrations greater than 1,000 mg/kg in shallow soils in areas where fertilizer products were handled or spilled. Ammonium is present in both on-site downgradient monitoring wells at ` concentrations of about 200 mg/1. Therefore, ammonium is a significant site contaminant that is contributing to groundwater degradation. In the late 1980s,underground storage tanks were removed and soils were excavated to a depth of 25 feet bgs. As reported in the 1998 Assessment, 300 cubic yards of nitrogen contaminated soil were removed in construction of new dry overhead bins in 1995. WFS also maintains a septic tank and leach .. field on the property. WFS needs to provide a diagram depicting where these soil excavations took place, show the septic system on a map, and provide a cleanup plan for removal of nitrate and ammonium from soil. If WFS chooses to explore remedial options for nitrogen removal that do not `— include excavation,then it needs to provide a feasibility study outlining various options. The lateral and vertical extent of ammonium and nitrate in the stormwater pond and tank farm are well �- defined,while the vertical extent of ammonium in the rinse pad area and lateral extent of ammonium in shallow soils where spills occurred are not well delineated. However, WFS can incorporate such delineation into either a cleanup plan or with confirmation samples following remediation. Groundwater Plume Delineation WFS has delineated the lateral and vertical extent of most groundwater pollutants. In the shallow groundwater,nitrate and ammonium extend off-site to downgradient MW s 0.05 ug/1, of about 1 and The volatile compounds 1,2-DCP and 1,2,3-trichloropropane are present in MW-5 at concentrations WFS obtained respectively, and extend beyond MW-5 under the adjacent agricultural field. In 1997, plume CPT groundwater samples along the perimeter of this field and found that the 1,2-DCP plume is narrow and does not extend beyond the field. The groundwater monitoring data to date has not included analyses for two constituents that were detected in soil at depths of 10 feet or deeper: dinoseb and toluene. Therefore,the draft monitoring and reporting program includes the corresponding analytical suites for these two compounds for two consecutive sampling events in the downgradient wells. If these constituents are not detected, they may be removed from the monitoring schedule. In March 1998, from the cond water bearing feetgs and pollutants wee not detected.ed CPT samples heefoe, WFS has delineated the formation ertical extent oof of 90 pollutants. On-site and off-site water supply wells were sampled and contaminants of concern were not detected. Summary While a few data gaps are present in characterizing soil and groundwater contaminants, these data gaps ` are predominately at the rinse pad and stormwater ponding areas. Since WFS has implemented an in situ pilot study in this area to evaluate the effectiveness of inducing reducing conditions to remediate pollutants,WFS may complete the characterization of soil contaminants when the pilot study is concluded,and incorporate the characterization into the cleanup plan. The monitoring and reporting program addresses additional groundwater constituents that may be present. Further characterization as