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2.8 Sample Container Cleanliness and Decontamination column. A low-Flow or low-permeability probe is defined as a condition where 1. New containers should be shown to be free of contaminants by providing data the minimum flow rate(100 mUmin)could not be sustained at the maximum from either the supplier or the analytical laboratory. applied vacuum level(I 0o inches water). See Appendix D for sampling protocols for low-permeability soils. follows: 2. After each use,reusable sample containers should be decontaminated as 3. Soil Gas Sample Collection using Sorbents for Method TO-17:Soil gas sampling for analysis by Method TO-17 is described in Appendix E and F. A. Glass syringes or bulbs should be disassembled and baked at 240°C for Low permeability materials may result in a lower Bow rate. Use of vacuum a minimum of 15 minutes o be d C fora minimum of 30 minutes,or be gage is recommended between the sorbent and extraction device. decontaminated by an equivalent method. If a syringe is re-used,it should Permeability testing of soil is recommended to determine the optimal flow rate be blank tested,and tested for adsorptive losses via spike testing. Blank at a vacuum of less than 100-inches of water(McAlary at a1:2009). TO-17 is testing frequency(or certification frequency)of syringes should also be currently recommended only for naphthalene analysis;however,TO-17 may • included in the workplan. also be used for other volatile constituents depending,on the DQOs for the project. The regulatory agency should be notifed and concurrence is B. SUMMA°canisters should be properly decontaminated as specified in US required prior to implementation of sorbent/TO-17 for other volatile EPA Method TO-15,and/or should be certified according to project DQOs, constituents other than naphthalene. either be batch or individually certified. 3.0 Field Conditions C. Tedlar`bags may be reused if data are provided to show the bags are Field conditions,such as rainfall,irrigation,fine-grained sediments,or drilling free of contaminants. conditions may affect the ability to collect soil gas samples. D. Equipment blanks should be analyzed to verify and evaluate the 1. Rainfall and Barometric Pressure(see Appendix Rainfall decreases effectiveness of decontamination procedures for recycled or reused the air-filled porosity of the shallow sail,thereby limiting diffusion transport of containers. At a minimum,one equipment blank should be run per 20 sample containers cleaned or at least one per day. volatile contaminants t so potentially biasing soil gas sampling results. Hence,do not conduct soil gas sampling during or within five days of a significant rain event(1/2 inch or greater). Stop irrigation or watering of soil at 2.9 Sample Collection least five days prior to the soil gas sampling event. Likewise,areas subject to soil gas sampling should be free of standing or ponded water for at least five 1. Vacuum Pump:When a vacuum pump is used,collect samples on the intake days prior to sampling. Do not perform soil gas sampling in swales or side to prevent potential contamination from the pump. Use a lung box when depressionswhere large volumes of water can potentially accumulate. collecting samples using Tedlar°bag(see Appendix C,Figure C-1). Record Barometric pressure Fluctuations associated with the passage of frontal vacuum readings and corresponding Flow rates on field data sheets for each sample.If the pump is battery operated,the batteries should be checked systems.can introduce atmospheric air into the shallow nodose zone. • before and during operation to insure a proper charge is maintained. Therefore,soil gas sampling should be delayed until Frontal systems have passed the area.Alternatively,soil gas sampling times and depths may be 2.. Soil Gas Sampling in Low-Permeability Soil:Soil gas sampling from low chosen to minimize the effects of changes in barometric pressure. permeability material(i.e.,silt and clay-rich soils)is feasible and high quality 2. Wet Conditions:If no-flow or low-Flow conditions are caused by wet soils due data can be produced with:(1)good annular seals;(2)careful monitoring of to a rain event or irrigation-flor water is drawn into a probe,cease the soil gas flow and vacuum during purging and sample collection;and(3)using tracer sampling. Low or no-flow condition corresponds to cases where the minimum gas i.e.,helium)for leak-testing. If the soil gas permeability is too low to flow rate of 100 mUmin cannot be sustained at the maximum applied vacuum allow sustainable purging at appreciable Flow rates without applying excessive vacuum,follow the protocols as described in Appendix D. An"appreciable of 100 inches of water(McAlary at al.,2009). If the low-flow condition is due flow rate"is defined as Flow of 100 mUmin or greater,and an"excessive to wet conditions or shallow groundwater,then passive samplers may be vacuum"is defined as any vacuum greater than about 100 inches of water deployed to detect VOCs. 3/3/2010 -29. 3/3/2010 -30-