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Subsurface Results <br /> Byron Road Trenching Alignment, Tracy California <br /> 3. Analytic Results <br /> 3.1 Analytic results from soil samples indicate that soil along the trench alignment <br /> between boring B-1 and B-9 (stations 99 +00 to 90 +00) is impacted with low <br /> levels of hydrocarbons. Ground water samples were reported as non-detect for <br /> these borings (Figure 2, Appendix A). <br /> 3.2 Soil samples from the trench alignment starting at B-10 through B-17 (stations <br /> 89 +00 to 81 +00) were impacted with hydrocarbons. Results ranged up to <br /> 2,200 ppm in the motor oil range (heavy hydrocarbons). <br /> 3.3 Ground water samples collected from B-10 through B-17 contained hydrocarbons <br /> at levels up to 850 ppb in the gasoline range. The laboratory noted that the <br /> results for this sample (from B-1 5) were associated with heavier hydrocarbons. <br /> 3.4 Four of the five analyses completed for PNA/PAH hydrocarbons did not detect <br /> levels of any of these compounds. One sample, from soil at 9 ft below grade in <br /> boring B-15, contained 2.8 ppm of 2-methylnapthalene. <br /> 4. Conclusions & Recommendations <br /> 4.1 Results of field observations, OVM readings, and analytic results indicate that soil <br /> along the planned trench alignment is impacted with hydrocarbons. The <br /> hydrocarbons were reported mostly in the diesel and motor oil range and can be <br /> characterized as degraded and weathered. Ground water along the trench <br /> alignment is impacted with hydrocarbons at locations west of B-9. <br /> 4.2 Field monitoring data collected from the PID noted readings in the deeper soil and <br /> water samples from borings B-13, B-14, and B-15. The field monitoring <br /> instrument is less sensitive to the heavier range hydrocarbons than to light <br /> (gasoline-range) hydrocarbons. The field readings noted from borings B-13, B-14 <br /> and B-15 indicate that hydrocarbon vapors will be encountered if the trenching <br /> work extends to depths below about 5 ft., especially at locations west of boring <br /> B-9, or station 89+00. <br /> 4.3 Due to the presence of hydrocarbons along the planned trench alignment, worker <br /> safety measures should be implemented to limit potential exposure to soil, water <br /> Page 3 of 4 <br />