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April 20, 1990 <br /> l <br /> i <br /> SANIPLE COLLECTION <br /> This section describes the routine procedures followed by G-R while <br /> collecting ground-water samples for chemical analysis These <br /> procedures include decontamination, water-level measurements, well <br /> purging, physical parameter measurements, sample collection, sample <br /> preservation, sample handling, and sample documentation Critical <br /> sampling objectives for G-R are to <br /> I Collect ground-water samples that are <br /> ` rei)resentative of the sampled matrix and, <br /> 2 Maintain sample integrity from the time of sample <br /> collection to receipt by the analvtical <br /> laboratory <br /> Sample analyses methods, containers, preservation, and holding times <br /> are presented in Table I <br />' Decontamination Procedures <br /> All physical parameter measuring and sampling equipment are <br /> decontaminated prior to sample collection using Alconox or equivalent <br /> detergent followed by steam cleaning with dcionized water Any <br /> sampling equipment surfaces or parts that might absorb specific <br /> contaminants, such as plastic pump valves, impellers, etc , are <br /> cleaned in the same manner <br /> Sample bottles, bottle caps, and septa used for sampling volatile <br /> organics arc thoroughly cleaned and prepared in the laboratory <br /> Sample bottles, bottle caps, and septa are protected from all <br /> potential chemical contact before actual usage at a sample location <br /> C <br /> During field sampling, equipment placed in a well are decontaminated <br /> before purging or sampling the next well The equipment are <br /> decontaminated by cleaning with Alconox or equivalent detergent <br /> followed by steam cleaning with deionized water <br /> C <br /> Water-Level Measurement <br /> Prior to purging and sampling a well, the static-.;ater levels are <br /> measured in all we]Is at a project site using an electric sounder <br /> and/or calibrated portable oil-water interface probe (Figure 4) Both <br /> static water-level and separate-phase product thickness are measured <br /> to the nearest ±0 01 foot The presence of separate-phase product is <br /> confirmed using a clean, acrylic or polyvinylchloride (PVC) bailer, <br /> measured to the nearest TO 01 foot with a decimal scale tape <br /> 7fLeffler — ryan Enc {415) 7837500 <br /> a)eneral and environmental coniraciors <br /> Page 12 <br />