SITE INFORMATION AND CORRESPONDENCE_FILE 2

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Page 1 of 2 Vicki McCartney [EH] From: Dinesh Rao [dinesh@amiadini.com] Sent: Monday, January 24, 2011 12:29 PM To: Vicki McCartney[EH] Cc: 'Larry'; 'Yarone (Ron) Madnick' Subject: FrontierTransport_p01_Field Duplicate-8260 vs T015 Attachments: Soil Gas Advisory Draft 2010.pdf Hi Vicki, As you are aware, I am assisting our permitting department with the questions and concerns you have on EPA Method 8260 vs TO15. This to explain our rationale for proposing EPA 8260 but we will be glad to use TO15 to satisfy your requirement. Attached is a copy of the March 2010 DTSC Advisory (Soil Gas Advisory) that we have been using to do our soil gas sampling. Section 3.4 (2) on page 35 describes the field duplicate sampling procedures but there is no mention of analyzing the duplicate sample with TO15. Table I on page 37 specifies EPA method 8260 among other methods that can be used for soil gas analysis. In Appendix F, Section F-5, page 82, duplicate sampling procedures is again discussed and there is no mention of analyzing it by TO15. This advisory indicates that duplicate sampling is needed to evaluate the reproducibility of the sampling process. I reviewed the DTSC's 2005 Guidance for Vapor Intrusion (VI Guidance) and it recommends doing a soil gas survey as per DTSC Advisory dated 2003, which was updated in March 2010 as described above. In addition, the VI guidance indicates that duplicate samples must be analyzed using T015 to confirm the mobile laboratory detection limits and identify other contaminants of concern. The reasons for collecting and analyzing duplicate samples are different for the VI and soil gas advisories. The former pertains to indoor air quality and the later pertains to subsurface soil gas sampling. For the VI guidance, the scope of work is designed to evaluate indoor air quality where lower detection limits and more compounds on target list of VOCs are needed. This guidance may not apply to the subject site because the contaminants are common BTEX and lower detection limits could be an overkill for BTEX compounds. We could analyze the duplicate sample by TO 15 but there is a risk in doing so. T015 method is good on two conditions - when very low detection limits are needed and/or if additional VOCs need to be identified,both of which do not apply to the site. The first condition pertains to low detection limits. We believe low detection limits are not needed for this assessment. The previous soil gas assessment done in January 2000 indicated benzene concentrations upto 5.4 ppmv. At such relatively high concentrations, to use TO15 the lab has to dilute the sample aliquot thus producing higher detection limits which defeats the purpose of using TO15. The second condition is about identifying other VOCs. T015 is good when there is a need to identify hard-to-detect VOCs such as dioxins, acetones, vinyl chloride and chloromethane which could exist at chlorinated solvents sites, industrial sites, or landfills. The subject site is a regular gasoline/diesel UST site and the contaminants of concern are the regular BTEX. As is our practice, we carefully evaluate the applicability and practicality of advisories pertaining to soil 1/27/2011