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rmrr�>t 3.3 Soil Vapor Analytical Results A summary of the detected concentrations in the soil vapor samples is provided in Table 3. A copy of the soil vapor analytical laboratory report is presented in Appendix G. Soil vapor analytical results detected a total of 16 VOC analytes, which included various solvents and aromatic compounds typical of products and wastes found at automotive service/filling stations and dry cleaning facilities. The analytical results were compared to the DTSC California Human Health Screening Levels(CHHSLs),where applicable. Concentrations of VOCs were not detected in the soil vapor samples submitted for chemical analysis, except as follows: • PCE was detected in all five analyzed soil vapor samples ranging from concentrations of 39 to 42,000 micrograms per cubic meter(pg/m3). PCE concentrations in BV-4-5', BV-4- 15' and BV-5-15' exceeded the commercial land use CHHSL established at 603 ug/m3. The soil vapor concentration in BV-6-12'was below the commercial land use CHHSL of 603 Ng/m3 but above the residential land use CHHSL of 180 pg/m3. The soil vapor concentration in BV-5-5'was below the residential CHHSL of 180 Pg/m3. • TCE was detected in BV-5-15' and BV-4-15'; however, only BV-5-15' exceeded the commercial land use CHHSL established at 1,770 ug/m3. • Low-level concentrations of VOCs including 1,2,4-trimethylbenzene(TMB), 2-butanone, 4-ethyl toluene, 4-ethyl-2-pentanone, acetone, benzene, carbon disulfide, chloroform, isopropanol, styrene, toluene, trans-1,2-DCE, and m,p,o-xylenes compounds were detected in some or all of the soil vapor samples analyzed. The detected concentrations were below the residential and commercial CHHSLs, where established. 3.4 Quality Assurance/Quality Control The following is a summary of the QA/QC analytical results collected during this investigation. 3.4.1 Soil Vapor Vacuum and Leak Test Results As described above, a pre-purge vacuum test was conducted at each sample location by opening the purge canister for several minutes to evaluate the manifold connections for pressure drops. No obvious leaks were indicated. A leak test compound (isopropanol)was also used during the sample collection process. Isopropanol was detected in three of the five samples; however, the isopropanol concentrations reported were low, ranging from 110 to 5,900 pg/m3, where detected. The reporting of isopropanol at concentrations below 6 percent does not significantly compromise the data. A review of the analytical data for the leak check compound suggests that the soil vapor data is acceptable for its intended purposes. Soil vapor analytical results are presented in Appendix G. 3.4.2 Data Validation Summary The analytical laboratory data was reviewed by Bureau Veritas to establish its validity and to ensure the laboratory data was complete and accurate. Bureau Veritas verified that holding times for each analytical method were achieved and that the laboratory achieved the specific data quality objectives for each selected analytical method. Each of the analyzed grab-groundwater samples were noted by the laboratory as having a significant sediment fraction (which are typical of grab-groundwater samples)that ranged between approximately 10 and 20 percent by volume that may provide false positive TPH concentrations in a water sample. A review of the data validation process indicates that the laboratories completed the QA/QC activities required for the samples such as blanks, lab control samples, matrix spikes, and duplicates. No significant QA/QC issues were identified as noted in the laboratory reports 8 Project Number 99008-008321.03