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1 PRIVILEGED & CONFIDENTIAL <br /> a <br /> Quality Assurance/Quality Control <br /> To increase the confidence levels in the data obtained and minimize the likelihood that <br /> judgments were made from potentially erroneous data, a quality assurance/quality control <br /> (QA/QC) program was implemented. <br /> ' The program includes formal procedures for drilling, sampling, decontamination, <br /> instrument calibration, documentation of field activities and calculations, and peer review. <br /> Routine QC procedures were performed by the laboratory, and included daily calibration of <br /> instruments, percent surrogate recoveries, and analysis of matrix spikes and matrix spike <br /> duplicates. The laboratory reported the results to be within acceptable percent error with no <br /> results exceeding the laboratory-established control limits. <br />' Decontamination <br /> The hollow-stem augers were decontaminated prior to the advancing of the boring. The <br /> sampler was decontaminated between sampling intervals, using a bristle brush, with a <br /> trisodium phosphate (TSP) solution; this was followed by two tapwater rinses. The <br /> sampler was dried by air prior to use. <br /> Waste Disposal <br />' The soil cuttings and purge water produced during the site investigation were placed in <br /> DOT-approved drums and stored on-site pending analytical result. The soil cuttings and <br /> purge water were transported and recycled/disposed of by a licensed hauler in accordance <br /> with appropriate regulations. <br />' FIELD OBSERVATIONS <br /> Soils beneath the site consisted primarily of silty clays, silty sand and silts. Groundwater <br /> was encountered at approximately 60 feet bgs during drilling activities. Elevated PID <br />' readings and stained soil were observed in Boring B4 at depths between 35 and 55 feet <br /> bgs. A geologic cross-section is included as Figure 6. <br />' LABORATORY RESULTS <br />' Soil <br /> TPH-g in Soil <br />' Two samples collected from Boring B4 (B4-35 and B4-45) submitted for chemical <br /> analyses were reported by the laboratory to contain detectable concentrations of TPH-g, <br />' ranging from 1.3 ppm to 75 ppm, respectively. The samples from Boring B4 at 25 feet <br /> bgs and 55 feet bgs were reported not to contain TPH-g. The laboratory results are <br /> summarized in Table 2. Laboratory reports and chain-of-custody forms are included as <br /> Appendix D. <br /> 6 197501-Stockton <br /> 1 <br />