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<br /> December 29, 2016| Page A-2 <br /> File No. 0504-119-00 <br /> <br />Field screening results can be site specific. The effectiveness of field screening can vary with temperature, <br />moisture content, organic content, soil type, and contaminant type and age. <br />Groundwater Sampling <br />Groundwater samples were collected from the temporary well points consistent with the EPA’s low-flow <br />groundwater sampling procedures (EPA 2010; Puls and Barcelona 1996). Dedicated polyethylene tubing <br />and a portable peristaltic pump were used for groundwater purging and sampling. During purging activities, <br />water quality parameters, including pH, temperature, conductivity, dissolved oxygen, and turbidity were <br />measured using a multi-parameter meter equipped with a flow-through cell. Groundwater samples were <br />collected after (1) water quality parameters stabilized; or (2) a maximum purge time of 15 minutes was <br />achieved. During purging and sampling the purge rate did not exceed 400 milliliters per minute. Water <br />quality parameter stabilization criteria included the following: <br />■ Turbidity: ±10 percent for values greater than 5 nephelometric turbidity units; <br />■ Conductivity: ±3 percent; <br />■ pH: ±0.1 unit; <br />■ Temperature: ±3 percent; and <br />■ Dissolved oxygen: ± 10 percent. <br />Field water quality measurements and depth-to-water measurements were recorded on a Well Purging-Field <br />Water Quality Measurement Form. The groundwater samples were transferred in the field to laboratory- <br />prepared sample containers and kept cool during transport to the testing laboratory. COC procedures were <br />observed from the time of sample collection to delivery to the testing laboratory consistent with the QAPP. <br />