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3.0 CONFIRMATORY SOIL SAMPLING AND ANALYSIS Soil chemical testing results from former soil borings (MW-1, MW-1A, BH-1, and BH-2) advanced in ' the vicinity of the former USTs indicated that the lateral extent of petroleum hydrocarbon-affected soil extended a maximum of approximately 25 feet from the center of the former UST excavation. The results of an initial confirmatory soil boring (CSB-1) advanced within the former UST excavation boundary showed subsurface soils directly beneath the former USTs had been remediated through vapor extraction. To further assess the effectiveness of vapor extraction, three additional confirmatory soil borings (BH-3, ' BH-4, and BH-5) were advanced at the locations shown on Figure 3. Soil borings BH-3 and BH-4 were vertical borings advanced on the east and west sides of the former UST excavation boundary, respectively. Boring BH-5, located approximately 4 feet west of vapor extraction well EW-1, was ' inclined towards the south at 30 degrees from vertical and was advanced to assess subsurface soils underlying the adjacent building foundation. The following sections describe the scope and procedures employed during confirmatory soil sampling and analysis. The findings of the work are described in Section 4.0. 3.1 DRILLING AND SOIL SAMPLING Prior to initiating field activities, SEACOR applied for and obtained a soil boring permit from the S]CPHS. Soil borings were advanced by Great Sierra Exploration on August 19, 1993, under the supervision of a SEACOR geologist. Boreholes were advanced using hollow stem auger drilling equipment. Vertical soil borings BH-3 and BH-4 were advanced to a total depth of 40 feet bgs. Slant soil boring BH-5 was advanced to a total inclined depth of 37 feet or a true vertical depth of 32 feet bgs. During borehole advancement, relatively undisturbed soil samples were collected at five foot depth 1 intervals from five feet bgs to total depth for lithologic description and possible chemical analysis. Soil samples were collected by driving a 18-inch long modified California split-spoon sampler lined with three 6-inch long brass sample tubes. Upon retrieval, the sampler was disassembled and the soil was described according to the Unified Soil Classification System (USCS). The SEACOR geologist maintained a boring ' log describing the soil types encountered (see Appendix B). A representative sample from each sample interval was screened in the field for the presence of volatile organic compounds (VOCs) using a photo- ionization detector (PID). Screening was accomplished by placing approximately 10 grams of soil into a ziploc bag and sealing the bag. After approximately 30 minutes, the tip of the PID was inserted into the ziploc bag and the VOC concentration in the headspace above the soil was recorded. PID readings in parts per million (ppm) isobutylene equivalents were recorded directly on the boring log. A minimum of one soil sample tube from each 18-inch sample interval was retained for possible chemical analysis. The open ends of the selected brass tube were immediately covered with aluminum foil, fitted with plastic end caps and sealed with tape. Sample tubes were labeled to designate boring location, sample depth, and date collected and immediately stored in an ice-filled cooler. CONFMM.M 50014-005-01 5 II