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2.3 Further Assessment and Monitoring Upgradient was retained in August, 1994 and supervised the installation of two additional monitoring wells in September. Five soil samples from GT-1 (Figure 2) were selected for laboratory analysis, and all five contained both diesel and gasoline-range hydrocarbons. Total Petroleum Hydrocarbon (TPH) concentrations decreased downward from 7050 mg/kg at 35 feet to 104 mg/kg at 55 feet. Three samples were selected from GT-2 for analysis. A TPH concentration of 288 mg/kg was reported at a depth of 55 feet; no contamination was detected at 50 feet or 60 feet. Diesel was detected in the groundwater sample from both wells, and gasoline was also detected in the sample from GT-2. No hydrocarbons were detected in the groundwater sample from MW-1. Upgradient continued to monitor the groundwater contamination through 1995, but due to unusually high water levels, representative samples could not be collected after January 1995. Measurement of the depth to groundwater was done quarterly, and appears to have confirmed that groundwater flow is dominantly south at the site, suggesting that contaminants may have migrated off the site onto adjacent property. 3.0 PROPOSED ASSESSMENT Five borings will be drilled with a Mobile Drill B61 rig equipped with 8-inch hollow-stem augers. A drill rig is preferable to a push-point sampling device at this site because of the thick and extensive hardpan layer that is present between 55 and 60 feet below grade. All five borings will be drilled to groundwater so that hydropunch samples can be collected, and two of the borings will be completed as groundwater monitoring wells. The proposed boring locations are indicated in Figure 2. Boring #1 will be located within the inferred plume of contamination to provide data on contaminant concentrations upgradient of the former tank location. Soil samples will be collected at 5-foot intervals, screened for the presence of volatile hydrocarbons using a Photovac Microtip HL-2000 photo-ionization detector, described on the boring log, and then delivered to Excelchem's state-certified mobile laboratory for on-site analysis of total petroleum hydrocarbons in the gasoline and diesel ranges and BTEX. The boring will be drilled to the capillary fringe, and a hydropunch-type sampling device will be used to collect a groundwater sample. The augers will then be steam-cleaned before moving to boring #2. Drill cuttings will be placed on plastic sheeting for future disposal. Boring #2 will be drilled south of the former tank location and GT-2, on the adjacent property. The boring will be located beyond the probable limit of soil contamination, and will be drilled primarily to determine the downgradient extent of groundwater contamination. Soil samples from this boring will be archived, but it is likely that only the sample(s) from the capillary fringe will be analyzed unless contamination is evident in shallower samples during field screening. A hydropunch sample will be collected and immediately analyzed, and if no contamination is detected, boring#2 will be completed as groundwater monitoring well GT-4. If significant contamination is detected, boring #2 will be backfilled with grout and boring#3 will be drilled downgradient of#2.