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L4 LEEDSHILL HERKENHOFF,INC September 1990 RESULTS SOIL SAMPLING ' As discussed previously, three sod borings (SB21, S1322, and S1323), were installed, representative soil samples obtained, and analyses performed for both BTX&E and TPH as gasoline. Results from the soil samples are presented in Table 1. As illustrated in Table 1, soil samples collected from SB21 and SB23 indicate essentially ' no detectable levels of petroleum hydrocarbon constituents SB22 located between SB21 and SB23 was found to have no detectable BTX&E and TPH concentrations at a depth of 10 feet, elevated petroleum hydrocarbon contamination at 15 feet, reduced, although 1 detectable, hydrocarbon levels from 20 to 45 feet, and essentially non-detectable to very trace levels below 45 feet. ' A tabulated summary of these data, plus the previously collected soils data from this area, is presented in Table 2. This data indicates that the highest hydrocarbon contamination was detected in soil boring T135, which contained increasing TPH concentrations from a depth of 5 feet to 20 feet, drastically decreased concentrations at 25 feet, and non- detectable hydrocarbon contamination at 30 feet Laterally, the data indicates an elevated TPH concentration at a depth of 15 feet in S1322, located dust east of T85, however, no other borings indicated TPH contamination. Therefore, the soil contamination discovered to the northwest corner of the site appears to be isolated to the very immediate vicinity of T135 between a depth of approximately 5 and 25 feet. This data also verifies that this ' area is not a current groundwater contamination source area GROUNDWATER SAMPLING As discussed previously, a groundwater sample was obtained from MW6 Analyses were ' performed for BTX&E and TPH as gasoline. A summary tabulation of LH's groundwater sampling results are presented in Table 3. ' As illustrated in Table 3, the groundwater quality has remained essentially the same since July of 1989 when LH began its investigation of the site; no increasing and decreasing concentration trends are apparent. This indicates that there does not appear to be a continuing source of contamination present at the site This is further indicated by the similarity of the results from MW1 and its replacement MW6. Table 3 shows that the water sample collected from MW6, like its predecessor MW1, indicates low but detectable ' levels of petroleum hydrocarbons. 10