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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 3.2 Analysis of Soil Gas Samples or lateral location. The following should be considered if low flow conditions y persist: Details concerning the analytical methods,quality assurancelqualily control • (QA/QC),reporting,and laboratory certification are described in Appendix.F and evaluate site lithologic logs • H. collect new continuous soil core samples use alternate low flow sampling methods(see Appendix D) Target Compounds: • re-evaluate the need for the sampling location • use passive soil gas methods as described in Appendix A • collect and evaluate soil matrix VOCs sample using 5035/8260(Cal/EPA, Target compounds are commonly-found VOCs which should be considered 2004) _ during initial site investigation. 4. If moisture or unknown material is observed in the glass bulb or syringe, Organic Common Target Compound List cease soil gas sampling until the cause of the problem is determined and corrected. Halogenated 5. If refusal occurs during drilling,soil gas samples should be collected as 1, Bromochloromethane «e follows: 2. Bromodichloromethane 3. Bromomethane A. For sample depths less than five feet,collect a soil gas sample following 4, Carbon tetrachloride the precautions for shallow soil gas sampling(i.e.,Section 2.3,Sample 5. Chloroethane Depth&Sub-Slab.Investigation Methods;Section 2.5,Purge Volume Test; 6. Chloroform and Section 2.6,Purge/Sample Flow Rate and Applied Vacuum). 7, 1,1.Dichloroethane 8. 1,2-Dichloroethane B. For sample depths greater than five feet,collect a soil gas sample at the 9. 1,1-Dichloroethylene depth of refusal:. 10. cis-1,270ichloroethylene 11. trans-1,2-Dichloroethylene C. Install a replacement vapor well at least five(5)feel laterally from the 12. Dichlorodifluoromethane(Freon 12) original vapor well decommissioned due to refusal. If refusal still occurs 13. Dichloromethane(methylene chloride) after three tries,use alternate vapor well installation methods. 14. Tetrachloroethylene(PCE) • 15. 1,1,1,2-Tetrachloroethane 3.1 Chain of Custody Records 16. 1,1,2,2-Tetrachloroethane . 17. 1,1,1-Trichloroethane A chain-of-custody form should be completed reconstructing how and under what 18. 1,1,2.Trichloroethane circumstances samples were collected,and include any problems encountered 19. Trichloroethylene(TCE) during sample collection. U.S.EPA provides a complete description of chain-of- 20. Trichlorofluoromethane(Freon 11) custody and records management(USEPA,1998,1998a). The chain-of-custody 21, 1,1,2-Trichloro-1,2,2-tri8uoroethane(Freon 113) procedure is intended to prevent misidentification of the samples,tampering with 22. Vinyl chloride the samples during shipping and storage,allow easy identification of any tampering,and allow for easy tracking of sample possession. Samples should Aromatics and Oxygenates always be stored in a secure area. To avoid water damage of the chain-of- 31312010 31 313/2010 -32-