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Frontier Transportation, Inc B23502.01 October 16, 1996 Page 5 • Evaluated the field and analytical data and assess the extent of PPC migration in soil and groundwater; 0 Assessed the need for additional site characterization and/or identified appropriate corrective action(s); and • Prepared this technical report documenting the investigative procedures, summarize the findings, and presenting conclusions and recommendations. 4.0 INVESTIGATIVE PROCEDURES This site characterization consisted of a field investigation, a laboratory testing program, and preparation of a technical report. The activities summarized below are intended to be consistent with the requirements of the SJCEHD. General standard operating procedures (SOPs), relevant to the field and laboratory activities, are described in Appendix A. Specific details and any deviations from the SOPs are summarized in the following sub-sections. 4.1 Field Investigation: The field investigation consisted of drilling soil borings for soil sample collection, drilling borings for the installation of groundwater monitoring wells, collection of groundwater samples, and analyzing soil and groundwater samples in the laboratory for selected PPCs. 4.1.1 Soil Boring Locations and Soil Sampling Criteria: Twining collected soil samples from two hand augered soil borings to investigate soil beneath the former dispenser island and the former product piping. The soil samples were collected using a hand auger which was advanced to approximately 3 feet BSG. This sampling was conducted subsequent to the removal of the product delivery lines by an excavation contractor retained by Frontier. The date of product delivery line removal was not provided by Frontier personnel. Hand auger sample locations are shown on Drawing 4. The final number and location of these samples were adjusted in the field by Twining personnel due to the presence of concrete pavement and inactive electric lines which limited access to soil beneath the former dispenser and product piping. Additionally, Twining drilled three vertical soil borings (B-1 through B-3) and one angle boring (B-4) to investigate soil conditions around the former gasoline USTs location. The borings were drilled using a Central Mine Equipment model 75 (CME-75), mobile hollow- stern auger drill rig. Drilling services were provided by Twining's Drilling Services Division (C57 Contractors License No. 506159) under the supervision of a Twining geologist. Soil boring locations are also shown on Drawing 4. The vertical extent of PPC migration directly beneath the former gasoline USTs excavation was not investigated since the material used to backfill the excavation has not been properly compacted.