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3.8 Soil Gas Sample Analysis: are detected in the soil gas samples,fixed and biogenic gas(oxygen,
<br /> carbon dioxide,and methane)data should be obtained using a Thermal-
<br /> 1. VOC Samples:All VOC samples should be analyzed using only a Gas Conductivity Detector(TCD)or a hand-held instrument;
<br /> Chromatograph/Mass Spectrometer(GC/MS)method(e.g., EPA Method C. At petroleum contaminated sites(including oilfields),concentrated animal
<br /> 82608,used for analysis of soil gas samples, EPA Method TO-15,TO-17 or
<br /> equivalent),except at well-characterized sites(e.g.,VOCs are known to be facilities and operations,wetlands,landfills or other sites where the
<br /> present and confirmed based on previous GUMS analyses). A non-GC/MS presence of methane and/or hydrogen sulfide is suspected,soil gas
<br /> method(e.g., EPA Method 8021 B,used for analysis of soil gas samples)may samples should be analyzed For methane and/or hydrogen sulfide;
<br /> be used only for routine monitoring of VOC contamination at well- D. Al sites where use of chlorinated solvents with 1,4-dioxane is suspected or
<br /> characterized sites. Sample introduction methods(i.e.,TO-15,TO.17,.TO-
<br /> 13A,and modified GC methods such as EPA Methods 8015 an 8021)and known toexist,soil gas samples should be analyzed for 1.4-dioxane ata •
<br /> their advantages and disadvantages are further discussed in Appendix F. reporting limit which is health protective.
<br /> Detailed discussion is provided in Appendix E for specifics concerning soil 5. Auto samplers:Auto samplers for Method 5030/82608 are not
<br /> gas containing naphthalene. recommended;and therefore,this technique should not be used because
<br /> transfer of sample from a soil gas collection vessel such as syringes to
<br /> If during routine monitoring, new VOC(s)were detected by a non-GC/MS
<br /> method,then at least 10 percent of the samples with each newly identified another secondary container(See Appendix F). Furthermore,are,a VOA-vials)may result in sample loss
<br /> VOCs should be confirmed by a GUMS method. Thereafter,routine uto.samplers are not capable of
<br /> handling variable volumes of soil gas sample,especially larger sample
<br /> monitoring can resume with the non-GC/MS method,including the new
<br /> analyle(s). volumes,to adjust for the desired RLs for thesite-specificcompounds of
<br /> potential concern.
<br /> 2. VOCs: Identify all quantifiable VOCs and report all results 3.9 Methane and Hydrogen Sulfide Sampling Programs:
<br /> Include the estimated results of all Tentatively Identified Compounds[flCs]) If the presence of methane and/or hydrogen sulfide is suspected,they should
<br /> detected in the report. If TICs are identified,contact the regulating agency to also be included in the analytical plan.
<br /> determine whether additional action is required(e.g.,running additional
<br /> standards to quantify TICs)and whether the use of these estimated data for 1. Methane Sampling Program:Methane samples may be analyzed by a GC
<br /> risk evaluation is appropriate. using modified EPA Method 8015B, EPA Method TO-3,EPA 3C,or by Land
<br /> 3. Leak Check Compounds:All results should be reported as specified in Tech Gas Analyzer GA-90,Gas Emissions Monitor GEM-500,GEM-2000 or
<br /> Section 2.4 other appropriate hand-held instruments.
<br /> 4. Specific Compounds:Based on the site history and conditions,analyses for A. Reporting Limit:The RL for methane analysis should not exceed 500
<br /> specific compounds may be required by the regulating agency staff. y parts per million by volume(ppmv). •
<br /> Examples include: B. Methane Sample Containers:In addition to the gas-tight sample
<br /> containers previously specified in Section 2.7,Tedlar°bags may be used
<br /> A. In areas where USTs or fuel pipelines are identified,soil gas samples for collection of methane samples with a holding time of no more than 24
<br /> should be analyzed for oxygenated compounds e. hours.
<br /> ether(MTBE),ethyl tertiary butyl ether(ETRE),di-isopropyl ether(DIPEj
<br /> tertiary amyl methyl ether(TAME),tertiary butyl alcohol(TBA),and C. Methane Screening Level:When methane is detected a[1,000 ppmv or
<br /> ethanol]; more,additional sampling and/or further investigation is recommended to
<br /> identify the source(s).
<br /> B. At oilfield sites where semi-VOCs or total petroleum hydrocarbons(TPHs)
<br /> D. Fixed and Biogenic Gases:At sites where methane is investigated and
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