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Page 1 of 4 Vicki McCartney [EH] From: Vicki McCartney [EH] Sent: Thursday, February 03, 2011 11:17 AM To: 'Dinesh Rao' Cc: 'Larry' Subject: RE: Frontier_p0l_Applicability of Vapor—Phase Validation for EPA Method 8260 Dinesh: I have reviewed your comments listed below that support the removal of a vapor-phase validation check standard when analyzing soil gas samples by EPA Method 8260 using liquid-phase standards instead of gas- phase standards. I concur with your conclusion that a vapor-phase validation check standard is not necessary based on the cost incurred, and the dependability of reporting accurate soil gas results for benzene,toluene, ethyl benzene, total xylenes, and methyl tertiary-butyl ether using water-phase standards for the initial calibration curve, continuing calibration check and associated quality control by Method 8260. Please proceed with the soil gas investigation, omitting the requirement that the off-site laboratory include a vapor-phase validation check standard when analyzing the soil gas samples. I appreciate the time and energy it took to investigation this matter. Thank you. Vicki McCartney, Senior REHS San Joaquin County Environmental Health Department 600 East Main Street Stockton,California 95202 Phone: (209)468-9852 Fax: (209)468-3433 Email: vin ccartnevncicehd.coin From: Dinesh Rao [mailto:dinesh@amiadini.com] Sent: Thursday, February 03, 20118:48 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 usually on the heavier end of the VOC spectrum such as dichloromethane and dichloroethane. DTSC put in this 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 compounds are the standard BTEX and fuel oxygenates which are perfectly fine with liquid phase standards and labs have reported consistent high recovery rates all the time. Therefore, a matrix match standard validation is 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. 2/3/2011