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• RESULTS OF INVESTIGATION: SSI - PHASE ONE SUBSURFACE CONDITIONS - SOIL vertical and lateral extent of impacted soil, specific PROFILE requests from PHS/EHD, and subjective field criteria Including odors, discoloration, and PID The soil profile at the site was previously readings TPHg was detected in four of the 13 summarized in the Site Conditions Section,and samples analyzed at concentrations ranging from additional description is presented here Soil types 1 3 to 640 mg/kg The two highest TPHg encountered in the three borings are shown in the concentrations reported(640 and 570 mg/kg)were ' boring logs(Appendix A), and in the cross-section both from collected from boring HP-2 at depths of shown in Plate 6 Dark yellowish brown clayey 12 5 and 20 5 feet bgs, respectively BTEX silt and sandy silt are present to depths ranging constituents were detected in the same four from approximately 14 0 to 17 5 feet bgs Beneath samples with benzene concentrations ranging from this silt horizon, fine- to medium-grained clayey 0 0095 to 5 3 mg/kg As shown in Table 3, none sand extends to the bottom of borings HP-1 (21 of the five fuel oxygenates or I,2-DCA were feet bgs) and HP-3 (25 5 feet bgs) Beneath the detected in the sample collected at 20 5 feet bgs in silt horizon in boring HP-3, alternating horizons of boring HP-2 silty sand, sandy silt, and sand extend to a depth of 27 5 feet bgs Below these horizons in boring HP- ANALYTICAL RESULTS - HYDROPUNCH I 2, a ten foot-thick layer of hard clayey silt extends GROUNDWATER GRAB SAMPLES to 37 5 feet bgs and is separated from twelve feet of very hard green silty clay in the bottom of the Analytical results from five Hydropunch samples boring by a five foot layer of fine to medium are listed in Table 2 Two samples each were grained sand Saturated soils were first collected from borings HP-1 and HP-3, and three encountered at depths of 3 5 to 4 5 feet bgs samples from boring HP-3 Hydropunch samples ' were collected at the first encountered Within boring HP-1, subjective hydrocarbon odors groundwater and at the bottom of borings HP-1 and elevated PID readings were only encountered and HP-3 In boring HP-2 the samples were in the sample collected at 15 5 feet bgs Within collected at first encountered groundwater(4 5 boring HP-2, subjective hydrocarbon odors were feet bgs), at 22 5 feet bgs, and at 31 feet bgs first encountered at 10 5 feet bgs(near the bottom Observations made during sampling indicated that of the former UST excavation) and extended to 41 free product was not present in boring HP-2 or in ' feet bgs Elevated PID readings(1 5 to 300 ppm) the other borings TPHg and BTEX constituents were encountered in all but the 5 5 and 55-foot were not detected above normal reporting limits in samples in boring HP-2 Within boring HP-3, any of the three samples collected at first subjective hydrocarbon odors and elevated PID encountered groundwater TPHg and BTEX readings were encountered in the samples constituents were detected in the remaining collected at 12 5 and 16 feet bgs Hydropunch samples TPHg concentrations ' detected ranged from 600 ug/L to 17,000 ug/L, ANALYTICAL RESULTS - SOIL SAMPLES and benzene concentrations ranged 3 5 to 440 ug/l The highest TPHg and benzene concentrations Analytical results from 13 soil samples are listed detected(17,000 ug/L and 440 ug/L)were in Table 2 and TPHg concentrations are plotted on collected from the sample collected at the screened PIates 4 and 6 Copies of the laboratory analytical Interval of 31 to 34 feet bgs in boring HP-2 As reports and chain of custody forms are included in shown in Table 3, none of the five fuel oxygenates 1 Appendix D Four samples each were submitted or 1,2-DCA were detected in the sample of first from borings HP-1 and HP-3, and five samples encountered groundwater(HP-2WA)collected 4 5 from boring HP-2 Sample selection was based on feet bgs in boring HP-2 As previously discussed ' the objective of completing the delineation of the these data suggested that increasing concentrations L 1300001387371WP138737N19 Harding Lawson Associates 12