SITE INFORMATION AND CORRESPONDENCE

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Ms. Wendy L. Cohen, Chief - 3 - 5 March 2003 methane were detected. Diuron and 1,2-DCP are also found in groundwater in the proximate monitoring well (MW-2). Monitoring well MW-2 also contains oryzalin and the fumigants ethylene dibromide (EDB) and dibromochloropropane (DBCP), but these compounds were not included in the soil analyses performed in 1990. At the conclusion of the pilot study, WFS will need to resample the soil in the stormwater pond and rinse pad areas to the depth of groundwater in order to identify if contaminants are still present in the soil column at concentrations requiring remediation and to test for oryzalin and fumigants. Other locations in which pesticides were detected included another dry well, located upgradient of MW-3, and in areas where soil staining was observed. In areas of soil staining, pesticides were detected at concentrations below the designated levels between one and two feet bgs, and not detected at five to six feet bgs. In the dry well, diuron was detected at a concentration above the designated level at 1-2 feet bgs but was not detected below that to the depth of sampling which was 10 feet bgs. Diuron does, however, appear at a concentration of about 1.5 ug/1 in downgradient monitoring well MW-3. This concentration does not exceed the water quality limit of 14 ug/l, but is above the background concentration of less than 1 ug/l. WFS also searched for this dry well but did not located it in the 1998 Geophysical Survey. The volatile organic compound 1,2-DCP is detected in off-site downgradient monitoring well MW-5 and on-site monitoring well MW-2, which is downgradient of the rinse pad in the northern corner of the site, but not in on-site monitoring well MW-3. Between MW-2 and MW-3 is the new tank farm. In my 13 February phone conversation with Ms. Bishop and Ms. Carolyn Kneiblher of GeoSyntec, Ms. Kneiblher pointed out data obtained from a May 1997 cone penetrometer test (CPT) investigation that showed 1,2-DCP is not widespread off-site in this area and that the source area for this compound is the northern corner of the site. I questioned whether the source could also be from beneath the new tank farm. Ms. Bishop stated that 1,2-DCP, which was present in Telone II, has never been stored at the new tank farm, which was constructed in about 1995. The Agency for Toxic Substances and Disease Registry reports that use of 1,2-DCP as a soil fumigant was disallowed in the early 1980s. Therefore, I concur that the source of 1,2-DCP is in the northern corner of the site, not beneath the new tank farm. While the vertical extent of pesticides in soil at the rinse pad and stormwater ponding areas is not yet defined, and it is unknown if fumigants and oryzalin are present in the soil column,the nature and extent of pesticide contaminants in the remainder of the site is delineated. The results of the pilot study will determine if reducing conditions are suitable for degradation of these pesticide compounds, and WFS will resample these areas to determine if constituents are still present, and if so, at what depths. In its evaluation of the pilot study, WFS will address remediation of pesticide compounds remaining in this northern area. Distribution of Fertilizers in Soil The 1990 Investigation also analyzed shallow and deep soils for nitrate and ammonium in areas where fertilizer products were handled and in a few locations where products were not handled. The results show that ammonium is the predominant form of nitrogen, and it is found at concentrations exceeding 1,000 mg/kg at depths of at least 10 feet bgs in the stormwater pond area, the former fertilizer tank farm, and both dry wells. Nitrate is also present at concentrations exceeding 1,000 mg/kg,but its extent is not as deep in the soil profile as ammonium. The 1995 Investigation confirmed ammonium throughout the soil profile in the former fertilizer tank farm and in the old tank area. At the rinse pad, ammonium was