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r 3.2 Phase 2—Extent of Contaminated Soil In July 1997, PHS/EHD held a meeting at the County office with Mr. Peters and requested him to submit a new work plan to continue the assessment of the contamination. On behalf of Mr. Peters, Upgradient Environmental submitted a work plan to drill five borings, including four monitor wells, in the second phase of assessment. This plan was amended in February 1998 and again in April 1998, as a result of information obtained when the two underground storage tanks were removed from the site. In the April amendment, the objective of the second phase was changed from an assessment of soil and groundwater contamination to a more limited assessment of soil contamination. 3.2.1 Tank Removal Results The 10,000-gallon tanks were removed by SEMCO, Inc., and Upgradient Environmental witnessed the removal and prepared the Tank Removal Report(March 30, 1998). The tanks were not replaced, and the tenants of the property ceased selling gasoline at that time. Although neither tank was excessively rusted nor damaged, four holes were found, one in each end of both tanks. The sandy backfill material near the ends of the tanks was badly discolored with petroleum, but the native clay beneath the backfill material appeared to be only slightly stained and relatively uncontaminated. Soil samples collected from the clay at the ends of the tanks confirmed the visual observations: petroleum hydrocarbons were present at low to moderate concentrations in all four samples from the base of the excavation and at low concentrations in the six samples from the excavated soil (Table 4). In addition, because groundwater entered the excavation during the removal and a (gasoline) sheen was apparent on the surface of the standing water, a bailer was lowered into the excavation and two water samples were collected. Hydrocarbons were detected in both samples at concentrations that considerably exceeded those found in the monitoring wells. The evidence of soil contamination around the tanks led to focusing the second phase of drilling on determining the extent of soil contamination. 3.2.2 Installation of Soil Borings In the second phase, five borings were drilled around the perimeter of the former tank cavity and soil samples were collected at variable intervals, generally starting near the base of the former tank cavity (15 feet). The borings were drilled with a truck-mounted Geoprobe® rig, and were not converted into monitoring wells. The soil' samples were analyzed for TPH-g, BTEX, gasoline oxygenates (including methanol at the request of PHS/EHD), total organic carbon (TOC), bacterial abundance, hydraulic conductivity, and porosity. The results of this phase of investigation were reported in the First Quarter 1998 Report (M�ty 30, 1998). Fourteen soil samples were analyzed, ranging in depth from 15 to 36 feet (Table 2). The results were quite similar to those obtained from the first phase of drilling: minimal evidence of soil contamination, mostly in the form of benzene. A hydrocarbon isocontour map was prepared (Figure 3