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Page 1 of 4 a V. . • Vicki McCartney [EH] From: Dinesh Rao [dinesh@amiadini.coml Sent: Thursday, February 03, 2011 8:48 AM To: Vicki McCartney [EH] Cc: 'Larry' Subject: Frontier_p01_Applicability of Vapor_phase Validation for EPA Method 8260 Vicki, I looked into your request to conduct a vapor phase validation check standard for the soil gas samples if a liquid- phase standard is used for EPA Method 8260. I read the calibration and validation sections (pages 73 and 74 in Appendix F) of the 2010 DTSC Advisory and I believe this requirement does not apply to our case. The advisory recommends doing a vapor-phase validation check because some compounds do not transfer readily from the liquid to gas phase. These compounds are such as dichloromethane and dichloroethane. DTSC put in this usually on the heavier end of the VOC spectrum requirement to ensure such exotic compounds do not get missed out when liquid-phase standards are used. This requirement also takes care of insoluble compounds such as dioxins or furans. However, at our site the target id phase standards and compounds are the standard BTEX and fuel oxygenates which are perfectly fine with liqu labs have reported consistent high recovery rates all the time. Therefore, a matrix matchistandard validation i3 really not required for BTEX and oxygenates at LUST sites such as ours. A vapor phase validation check is "reasonable and necessary" if one is doing an initial baseline survey where the source of contamination is not known but our site is a regular LUST site with hydrocarbon fuels. I believe EPA Method is 8260 using liquid-based standards is perfectly fine for the BTEX and fuel oxygenate compounds at our site. I spoke to the TEG Soil Gas lab in Sacramento (lab contracted to do soil gas analysis for the site) and H&P Mobile Geochemistry lab in San Diego and they indicate that most labs in California are not doing the vapor- phase validation check because the difference in value is not significant for BTEX and oxygenate compounds. In addition,the cost of a single standard is $75 and assuming 70 VOCs on the list, the cost of one validation check will be approximately$6,000. Add to that the cost of using a second standard to check the first standard as stated in the 2010 DTSC advisory and we end up with a cost of$12,000 for doing the vapor-phase validation check for this project. It will be hard to justify the high cost to the client and the UST Cleanup Fund because the improvement to data quality is insignificant. As I was reading the 2010 Advisory I noticed that there is an inconsistency in percent recovery during validation of calibration curve. On page 73, it says the percent recovery should be less than 20% and on page 74 it says it can be upto 30%. I bought this to the lab's attention and they said this is one of the many inconsistencies in the procedures described in Appendix F. I believe this is one of the bigger issues that DTSC and labs are trying to work out and a better and accurate validation procedure will be described in the final advisory. Your second request related to ensuring the reporting limits are below the ESLs or CHHSLs for residential land use. Our lab is able to meet this requirement. In conclusion, we believe that soil gas sample analysis by EPA Method 8260 using liquid-based standards is perfectly ok for the BTEX and fuel oxygenate target compounds at the site and it will meet the data quality objectives for the proposed risk assessment. Also, the reporting limits for EPA Method 8260 will be below the ESLs or CHHSLs. Understanding that the DTSC advisory is only a guidance not a regulation, we sincerely request that you consider the site background, our data quality objectives, target compounds, and re-evaluate the applicability of your request for vapor-phase validation and let us know if we can proceed with analyzing soil gas samples with the 2/3/2011