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Sampling point SV-1 was sampled and analyzed three times after one, three, and seven purge volumes were expelled from the sampling train as per DTSC protocols. The purge volume used yielding the highest analytical results would indicate which purge volume to use prior to collecting the remaining soil vapor samples. The analytical results were non-detect #- for all analyzed compounds at all purge volumes. As a result a default purge volume of three was used on all subsequent samples as per the DTSC protocols. �. Once sampled, the sample syringe was sealed by closing an attached valve, and transferred to the on-site mobile analytical laboratory and analyzed within two or three minutes in most cases and always within thirty minutes as per DTSC protocols. Since TPH-gasoline, BTEX components, MtBE, and lead scavengers are the volatile compounds that have been noted previously at the subject site, the soil vapor samples were analyzed for the following parameters: -- Total petroleum hydrocarbons as gasoline (TPH-gasoline) (EPA method 8260); -- The aromatic volatile fuel components benzene, toluene, ethylbenzene, and xylenes (BTEX) (EPA method 8260); `' -- Fuel oxygenate methyl-t-butyl ether (MtBE) (EPA method 82606); -- The lead scavengers 1,2 dichloroethane (1,2 DCA) & 1,2-dibromoethane (EDB) (EPA method 8260). Additionally, since TPH-diesel has been found at the subject site, sorbent tubes were used to collect TPH-diesel compounds from soil vapor for analysis off-site by ALS Laboratory Group �. by pulling two liters of soil vapor through the sorbent tube with a vacuum pump immediately following soil vapor collection for the on-site mobile lab. A summary of the soil vapor results can be found on table III and the analytical laboratory data sheets can be found in Appendix B, LN 6.3 Soil Vapor Survey Conclusions The analytical results from the soil vapor samples collected from all six soil vapor locations were non-detect at or above the laboratory reporting limit for all on-site and off-site analyzed compounds. i' 6.0 EVALUATION OF SUBSURFACE VAPOR INTRUSION The lowest San Francisco Bay Regional Water Quality Control Board environmental �* screening levels (ESLs), from table E-2 (Interim Final — November 2007, SF Bay RWQCB), and the OEHHA California Health Hazard screening levels (CHHSLs) for the compounds analyzed in soil gas that have been present over the last two years in groundwater at the �. subject site are as follows: 4 Ir L 6 JJW GEOSCIENCES lnC.