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1 <br /> Ms Vicky McCartney <br /> Page 3 of 3 <br /> • <br /> Disc—ussion <br /> Dissolved benzene in groundwater at the site would not pose a significant health risk to occupants of a <br /> building overlying the plume of contamination, under either residential or commercial property use <br /> scenarios Although TPHg groundwater screening levels for vapor intrusion concerns are not published <br /> in the RWQCB document, dissolved TPHg should not be a concern at this site In the RWQCB <br /> document, Table E "Environmental Screening Levels fol Indoor An cind Soil Gas (Trapot Inuusion <br /> Concerns)" includes indoor air and soil gas ESLs for both benzene and TPHg The values of the ESLs <br /> for TPHg are 250 to 300 tines higher than the ESL values for benzene Since the level of dissolved <br /> TPHg in groundwater at the site is similar to the level of benzene and the fact that the benzene level is <br /> two orders of magnitude below the ESL, it can reasonably be concluded that TPHg would not pose a <br /> significant health risk. The pertinent tables from the RWQCB document are included in Attachment A <br /> CONCLUSIONS <br /> The average concentrations of residual gasoline and benzene in groundwater at the site do not exceed <br /> residential or commercial property use screening levels for vapor intrusion concerns <br /> No furthei evaluation of this potential exposure pathway is needed If you have any questions or <br /> comments please contact us at your earliest convenience <br /> Respectfully, <br /> Ground Zero Analysis, Inc5�01 SFO <br /> �'w <br /> Gregory P Stahl PG 5023 R <br /> CA Certified Hydrogeologrst No 264 <br /> AttachmentsCAV�O�` <br /> cc Ms Jan Thompson, Wilbur-Ellis <br /> Mr Eric Jenks, Wilbur-Ellis <br /> Mr Doug Reynolds, H&H Engineering <br /> Mr James L L Barton,RWQCB <br /> r <br /> G 1GROUNDZENW DRiSKV HARSEGWTv doc <br />