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3. Fine Grained Soil: If low-flow or no-flow conditions are caused by fine- custody forms during transport,the forms should be placed into a water-tight grained soil,clay,soil with vacuum readings that exceed approximately 136 sealable bag and placed on top of the sample container. inches of water or 10 inches of mercury are encountered at a sampling point, a new vapor well should be installed in a coarser lithology at a different depth or lateral location. The following should be considered if low flow conditions 3.2 Analysis of Soil Gas Samples persist: Details concerning the analytical methods,quality assurance/quality control • evaluate site lithologic logs (QA/QC),reporting,and laboratory certification are described in Appendix F and • collect new continuous soil core samples A " H. ,r • use alternate low flow sampling methods(see Appendix D) • re-evaluate the need for the sampling location Target Compounds: • use passive soil gas methods as described in Appendix A sf • collect and evaluate soil matrix VOCs sample using 5035/8260(Cal/EPA, 2004) Target compounds are commonly-found VOCs which should be considered ji during initial site investigation. R _ 4. If moisture or unknown material is observed in the glasshulb or syringe, a ' cease soil gas sampling until the cause of the problem is determined and Organic Common Target Compound List corrected. � Halogenated 5. If refusal occurs during drilling soil gas samples should be collected as follows: 1. Bromochloromethane lxr 2. Bromodichloromethane A. For sample depths less than five`feet,collect a soil gas sample following 3. Bromomethane the precautions for shallow soil gas sampling(i.e.,Section 2.3,Sample 4. Carbon tetrachloride Depth&Sub-Slab Investigation Methods;Section 2.5, Purge Volume Test; 5. Chloroethane and Section 2.6, Purge/Sample Flow Rate and Applied Vacuum). 6. Chloroform ` 7. 1,1-Dichloroethane '`3 B. For sample depths greater than five feet,collect a soil gas sample at the 8. 1,2-Dichloroethane depth of refusal. 9. 1,1•Dichloroethylene 10. cis-1,2-Dichloroethylene C. Install a replacement vapor well at least five(5)feet laterally from the 11. trans-1,2-Dichloroethylene original vapor well decommissioned due to refusal. If refusal still occurs 12. Dichlorodifluoromethane(Freon 12) after three tries,use alternate vapor well installation methods. 13. Dichloromethane(methylene chloride) 14. Tetrachloroethylene(PCE) 3.1 Chain of Custody Records 15. 1,1,1,2-Tetrachloroethane 16. 1,1,2,2-Tetrachloroethane A chain-of-custody form should be completed reconstructing how and under what 17. 1;1,1-Trichloroethane circumstances samples were collected,and include any problems encountered 18. 1,1,2-Trichloroethane during sample collection. U.S.EPA provides a complete description of chain-of- 19. Trichloroethylene(TCE) custody and records management(USEPA,1998, 1998a). The chain-of-custody 20. Trichlorofluoromethane(Freon 11) procedure is intended to prevent misidentification of the samples,tampering with 21. 1,1,2-Trichloro-1,2,2-trifluoroethane(Freon 113) the samples during shipping and storage,allow easy identification of any 22. Vinyl chloride tampering,and allow for easy tracking of sample possession. Samples should always be stored in a secure area. To avoid water damage of the chain-of- Aromatics and Oxygenates 3/3/2010 -31- 3/3/2010 -32-