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Vicki McCartney [EH] From: Nuel Henderson [EH] Sent: Thursday, March 07, 2013 8:46 AM To: 'wlittle@advgeoenv.com' Cc: Vicki McCartney[EH] Subject: RE: GEO_REPORT Submittal#9194721996 : T0607700898 Has Been Denied Bill, The report was denied for errors in the report as detailed by Vicki in her denial of it; it was not denied because we disagreed with the conclusion - that has yet to be determined. Fix the errors, or show that they are not errors, and the report will be accepted onto GeoTracker. The HHRA issue posed by the benzene in soil gas must be addressed to show that human health is adequately protected. Your argument presented in this email would certainly be a part of the argument for the general case, but we need you to show us that the site specific conditions have been adequately addressed for now and into the future, such that the benzene in soil gas will not pose a threat to human health. Should some form of mitigation be put into place? Is additional soil gas assessment SW of the line formed by V100-102 needed? Show us that the soil gas issue is adequately characterized and under existing and anticipated future site conditions and use that the soil gas does not pose a threat to human health. Regards, Nuel -----Original Message----- From: William Little [mailto:wlittle@advgeoenv.com] Sent: Wednesday, March 06, 2013 2:57 PM To: Nuel Henderson [EH] ; Vicki McCartney [EH] Cc: rmarty@advgeoenv.com Subject: FW: GEO_REPORT Submittal #9194721996 : T0607700898 Has Been Denied Mr. Nuel Henderson: AGE prepared a model for soil vapor intrusion risk at the Lodi Airport site, 23987 HWY 99, ACAMPO, CA. Our results were very close the minimal cancer risk of 10-6. Text below provides a primer to a risk evaluation discussion our client would now like to pursue with your office. The small concentration of benzene in one soil vapor sample represents one area of the building on the site. A less conservative approach would be the reduction of the model input for benzene, by 50 8 based on the reduction or lack of petroleum on the remaining sides of the structure. RISK DISCUSSION For carcinogens, the human health screening levels presented are based on a target excess cancer risk of 10-6. This represents the upper end (most stringent) of the potentially acceptable range of 10-4 to 10-6 recommended by the USEPA (USEPA 1989a,b) . As stated in the National Contingency Plan, however, "The 10-6 level shall be used as the point of departure for determining remediation goals. . . " (USEPA 1994) . Remediation or risk management is rarely warranted at sites where the estimated cancer risk does not exceed 10-6. Remediation or risk management is almost always warranted at sites where the estimated cancer risk exceeds 10-4. For sites where the estimated risk is between 10-4 and 10-6, the need for active remediation or risk management is evaluated on a site-specific basis (i.e. , risks within this range are "potentially acceptable", depending on site-specific considerations) . Please re-evaluted your offices denial of the report of findings. Sincerely, 1