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collected to support the sampling activity: 4. Split Samples:The regulating agency staff may request that split samples be collected and analyzed by a separate laboratory. 1. Sample Blanks: A. Method Blanks:Method blanks should be used to verify the effectiveness 3.5 Laboratory Certification: of decontamination procedures and to detect any possible interference from ambient air. The California Department of Health Services, Environmental Laboratory Accreditation Program(ELAP)currently requires certification for soil gas B. Trip Blanks for Off-site Shipments:Trip Blanks are not necessary for analytical laboratories. Laboratories utilizing EPA Methods 8260B,8021 B, SUMMA'"canister samples. 80158,TO-15 and TO-17 for analyses of soil gas samples should obtain ELAP certifications for such EPA analytical methods accordingly. The regulating C. Soil Vapor well materials:An assembled soil gas probe,tip and tubing agencies or DTSC's Environmental Chemistry Laboratory(ECL)staff may should be blank tested prior to installation at a frequency of 1 installation inspect the laboratory. Further recommendations concerning laboratory per new batch of tubing used. certification are provided in Appendix F. D. Equipment Blanks: Equipment blanks should be collected from 3.6 Holding Time: decontaminated equipment before reuse at a frequency specified in the workplan. At a minimum,one equipment blank should be run per 20 All soil gas samples,with the exception of hydrogen sulfide samples,should be sample containers cleaned,or at least one per day. analyzed within 5 minutes of sample collection by an on-site mobile laboratory. Hydrogen sulfide samples should be analyzed as specified in Section 3.9(23). 2. Duplicate or Replicate Samples:Two samples must be collected Under the following conditions,holding times may be extended and analyses simultaneously for duplicate samples. Samples collected sequentially are performed off-site: replicate samples. At least one(1)duplicate or replicate sample should be collected and analyzed per 20 samples or per batch,whichever is more often. 1. Soil gas samples collected in glass bulbs with surrogates added within 15 Duplicate(or replicate)samples should be collected from contaminated areas minutes of collection may be analyzed within 6 hours after collection; at a frequency depending on the project DQOs. The frequency of duplicates (or replicate)per laboratory per day used by the mobile laboratory should be 2. Soil gas samples collected in glass-lined or silicon coated SUMMA'°canisters specified. There are other types of replicate samples,which may be valuable: may be analyzed within 14 days from collection(see Appendix B);and (1)spatial replicate(i.e.,sample collected at a similar depth a few feet from the investigative sample),and(2)temporal replicates(i.e.,sample collected 3. Methane samples may be analyzed as specified in Section 3.9. at the end of field activities from same depth and locations as the first sample)._ 3.7 Analytical Methods: A. Duplicate(or replicate)samples should be collected in separate sample containers,at the same location and depth. There are no approved U.S. Environmental Protection Agency(USEPA)methods specifically designed to analyze VOCs in soil gas samples. Consequently, B. Replicate samples can be collected immediately after the original sample modified versions of existing EPA methods were adopted to analyze VOCs in soil or a duplicate sample can be collected simultaneously by use of a splitter gas samples. (T)at the point of collection to divide the sample stream into two separate sample containers. There are numerous modifications of EPA methods being used for VOC analysis in soil gas in California. Each modification has its advantages and 3. Laboratory Control Samples and Dilution Procedure Duplicates: disadvantages. For general purposes,Table 1 below summarizes the preferred Laboratory Control Samples(LCS)should be done in accordance with the EPA methods and their modifications for soil gas analysis. These modifications discussion provided in Appendix F. are preferred because they provide the most reliable and defensible data based on generally accepted DQOs. 3/3/2010 -35- 3/3/2010 -36-