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Groundwater Sampling Using a Bailer SOP 4.0 Cautions and Interferences: Cautions associated with conducting this procedure include: • Before sampling, newly installed monitoring wells shall be allowed to stabilize for a minimum period of 24 hours or established state regulatory requirements after development. • Analysis can be compromised by field personnel in two primary ways: 1) taking an unrepresentative sample, or 2) by incorrect handling of the sample. • There are numerous ways of introducing foreign contaminants into a sample, and these must be avoided by following strict sampling procedures and utilizing trained field personnel. • As a general rule, all monitoring wells should be pumped(preferred) or bailed prior to sampling. • Ideally, sampling equipment should be completely inert, economical to manufacture, easily cleaned, sterilized, reusable, and able to operate at remote sites in the absence of power sources. • Materials of construction for samplers and evacuation equipment(bladders, pump, bailers, tubing, etc.) should be limited to stainless steel, Teflon, and glass in areas where contaminant concentrations are expected to be at or near the detection limit. The tendency of organics to leach into and out of many materials make the selection of materials critical for trace analyses. The use of plastics, such as PVC or polyethylene may be used for evacuation and sampling equipment. In highly contaminated wells, disposable equipment(i.e., Teflon,polypropylene, or PVC bailers)may be appropriate to avoid cross-contamination. • Materials of construction for sampling Per- and Polyfluoroalkyl Substances (PFAS) and evacuation equipment(bladders, pumps, bailers, tubing, etc.) should be limited to High Density Polyethylene (HDPE), silicone, stainless steel and/or polypropylene. The tendency of common sampling materials such as Teflon, Low Density Polyethylene (LDPE), and glass to contain PFCs make the selection of materials critical. All sample containers should be limited to containers made of HDPE or polypropylene. • PFAS samples should not be filtered in the field prior to being transferred into sample containers as glass fibers from the filter can potentially absorb PFAS. • PFAS sampling shall be conducted in accordance with the Groundwater Sampling for PFAS SOP. PFAS best practices are continually evolving and Antea Group policy is to contact Jack Sheldon or Caron Koll before conducting PFAS sampling. • Wells should be sampled as soon as possible after purging (certainly no more than 24 hours) and should be sampled in order from least contaminated to most contaminated or from upgradient to downgradient if chemistry is unknown. o Ideally, water levels shall be allowed to recover to 90% of the static water level before sampling. This may be altered if wells are very slow (i.e., days)to recharge so samples can be collected. o All non-dedicated equipment shall be decontaminated in accordance with Decontamination SOP prior to use or upon completion of the sampling activities. Control#:AG-10034-00 Page 4 of 9 File Name:Groundwater Sampling Using a Bailer SOP