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V Additional Soil and Groundwater Investigation and Monitor Well Installation Report CSUS Multi-Campus Regional Center January 11,2002 Page 8 5.4 INVESTIGATION RESULTS The results of the soil and groundwater investigation include field observations (PID sample screening results, detection of sample odors, and visual observations of site geology), soil and groundwater sample laboratory analytical results, and groundwater elevation measurements. 5.1 FIELD OBSERVATIONS Field observations included CPT boring observations, PID screening results, detection of sample odors, and visual observations of the site geology. Field observations are included on the geologic logs prepared for all of the borings (Appendix B). CPT borings CPTI, CPT2, CPT2-A, and CPT3 were advanced to depths of approximately 91 feet, 81 feet, 81 feet, and 83 feet bgs, respectively. Soils encountered by the borings were predominantly interbedded clays and silts with interspersed thin beds of sand. Several discontinuous beds of sand were encountered in the borings. CPT logs also indicate that beds of sand encountered at depths of approximately 13 to 13 feet, 38 to 43 feet, 53 to 58 feet, 69 to 71 feet, 73 to 74 feet, and 79 to 81 feet are continuous across the site. Three of these continuous sands were selected for discrete depth groundwater sampling intervals. Direct push borings GP-6, GP-7, GP-8, and GP-9 were advanced to depths of approximately 56, 61, 61, and 61 feet bgs, respectively. Soils encountered by the borings were predominantly clay and sandy clay, with sand and clayey sand near the bottom of the borings. PID measurements of samples from the borings indicated organic vapor concentrations of 6.0 to 754 ppm in GP-6, 0 to 31 ppm in GP-7, 0 to 372 ppm in GP-8, and 0 to 14.4 ppm in GP-9. Petroleum hydrocarbon staining of soils was observed in boring GP-6 and generally coincided with the PID measurements that indicated the presence of organic vapors. In borings GP-7, GP-8, and GP-9 it was not possible to distinguish between what may have been petroleum staining and the natural color of the soil. Monitor well borings MW-1, MW-2, and MW-3 were all advanced to a depth of approximately 45 feet bgs. Soils encountered by the borings were predominantly clay and sandy clay, with silty sand and clayey i' sand near the bottom of the borings. Samples of drill cuttings were collected in plastic zip lock bags and tested for organic vapors with a FID. No organic vapors were detected with the PID in samples from borings MW-1 and MW-3. Organic vapors were detected at a concentration of 2.4 ppm in one sample rr from the bottom of boring MW-2. No petroleum odor was noted in the groundwater purged from monitor wells MW-1 and MW-2 during well development or sample collection. A slight petroleum odor was noted in the groundwater purged from monitor well MW-3 during both well development and sample collection. 5.2 RESULTS OF LABORATORY ANALYSES As described in Sections 3.3.1, 3.2.2, 4.3, and 4.7 of this report, soil and groundwater samples from the direct push borings, soil samples from the monitor well borings, and groundwater samples from the monitor wells were submitted for laboratory analyses. The laboratory analytical results of the soil samples are presented in Table 2 and are shown in Figure 3, Appendix A. The laboratory analytical results of the groundwater samples are included in Table 3 and in Figure 4, Appendix A. Copies of laboratory L analytical results and chain-of-custody records for the samples are included in Appendix D. A discussion of the soil and groundwater sample analytical results is included in Section 7 of this report. A �' CONDOR