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z <br /> t ' <br /> 06 June 1997 <br /> AGE-NC Project No. 97-0327 <br /> Page 4 of 5 <br /> at concentrations as high as 5.0 parts per million (ppm). <br /> 4.3 ANALYTICAL RESULTS OF SOIL SAMPLES <br /> A total of five soil samples were submitted to a state-certified laboratory for analysis of TPH-g, TPH- <br /> d, BTEX and MTBE. The laboratory analysis did not detect TPH-g, TPH-d, benzene, toluene or <br /> ethylbenzene in the soil samples. However, MTBE was detected from soil samples collected in probe <br /> borings P-3 (25-feet), P-4 (30-feet) and P-5 (25-feet) at concentrations as high as 0.28 mg/kg <br /> (milligrams per kilograms or parts per million: ppm); xylenes were detected in a soil sample collected <br /> at P-4 (30-feet) at a concentration of 0.026 ppm. <br /> Analytical results of soil samples are summarized in Table I -Analytical Results of Soil Samples. The <br /> laboratory report (Castle Analytical Laboratory Reference No. I f 16) and chain-of-custody are <br /> included in Appendix B. <br /> 5.0. CONCLUSIONS AND SUMMARY <br /> Based upon field and analytical data collected at the site on 12 May 1997, AGE concludes the <br /> following: <br /> Low concentrations of petroleum hydrocarbons (MTBE and xylenes) were detected in soil <br /> samples from probe borings P-3 through P-5 at depths of 25 and 30 feet bsg. However, the <br /> concentrations of MTBE and xylenes are not much greater than the laboratory reporting <br /> limits. Therefore, it appears that soil impacted by trace levels of hydrocarbons in the UST area <br /> is limited in vertical extent to depths of approximately 25 to 30 feet bsg. <br /> • The estimated depth to ground water at the property is 70 feet bsg. <br /> The detected xylene is well below Maximum Contaminant Level (MCL) of the California <br /> Drinking Water Standards. <br /> • Although there is no MCL standard for MTBE, there is an established Action Limit (AL) with <br /> respect to California Drinking Water Standards. MTBE is a widely used gasoline additive <br /> (octane enhancer)that began to be used in California during the late I970's and early 1980's. <br /> MTBE is very water soluble, and appears to have a very slow biodegradation rate in ground <br /> water. The detection of MTBE suggests that a release may have occurred within the last 20 <br /> years. <br /> 4 Y� <br /> f� <br />