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1 <br /> 1 <br /> 5 samples had diesel concentrations in excess of the detection <br /> limit (1 ppm) . <br /> Gasoline was detected in sample S-11 at a concentration of 1, 100 <br /> ppm, and volatile aromatics were detected in this sample at 0. 35 <br /> ppm (xylenes) . Laboratory results are summarized in Table 4 . The <br /> laboratory report and chain-of-custody are included in Appendix C. <br /> 4 .3 Stratigraphy <br /> The generalized stratigraphic sequence in the borings consists of <br /> brown clay and clayey silt from the surface to 15 feet and brown <br /> silty sand from 15 to 20 feet. The borings bottomed in brown clay <br /> at 21 feet . Gray-green discoloration was noted from 10. 3 to 11. 2 <br /> feet, and organic vapors were detected in this sample. No organic <br /> vapors were detected in any other section of the boring (see <br /> attached boring logs - Appendix A) . <br /> 4 . 4 Analytical Results of Monitoring Well Samples <br /> I4 . 4 . 1 Soil Samples <br /> Petroleum hydrocarbons were detected in sample MW4-10 at levels of <br /> 120 mg/kg (TPH-g) and 38 mg/kg (TPH-d) . TPH as gasoline was also <br /> detected in sample MW4-15 at a level of 2 .2 mg/kg. No benzene was <br /> detected in the three samples analyzed from this boring, but <br />' toluene, ethylbenzene, and xylenes were detected at low <br /> concentrations (Table 3) . The laboratory results and chain of <br /> custody are included in Appendix B <br /> r4 .4.2 Groundwater Samples <br /> Petroleum hydrocarbons were detected in monitoring well MW-1 at <br /> levels of 2 , 300 ug/L (TPH-g) and 890 Ag/L (TPH-d) (parts per <br /> billion) . The analysis was repeated by the laboratory and a <br /> concentration of 520 ug/L TPH-d was obtained. Gasoline was also <br /> detected in the sample from MW-4 at 61. µg/L. <br /> Benzene and toluene were detected in monitoring well MW-1 at 21 <br /> ug/L and 5 . 0 ug/L, respectively. Ethlybenzene and xylenes were <br /> detected in samples from MW-1 and MW-4 . No contamination was <br /> detected in samples from MW-2 and MW-3 . The water sample analyses <br /> are summarized in Table 5 . The laboratory results and chain of <br /> custody are attached in Appendix D. <br /> 4 .5 Groundwater Elevation and Gradient <br /> The present depth to groundwater is between 9 and 12 feet. Based on <br /> depth-to-groundwater measurements in monitoring wells MW--1 to MW-3 , <br /> the hydraulic gradient was calculated to be 0. 0024 ft/ft directed <br /> N 140 w (Figure 3) . This result is consistent with the gradient in <br /> March 1993 and confirms that MW-4 is the most down-gradient well. <br /> 13 <br />