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4.7 Groundwater Sampling <br /> Prior to sampling, groundwater level measurements will be obtained in all wells to <br /> determine the groundwater depth and elevation. These measurements will also be used to evaluate <br /> the groundwater flow direction and gradient. Groundwater level measurements will be performed <br /> prior to purging and sampling activities at each well and will be recorded in a field logbook. The <br /> measurements will be obtained with an electronic water level sounder capable of obtaining <br /> measurements to the nearest +/- 0.01 foot. All water level measurements will be referenced to an <br /> established point at the top of each wellhead. <br /> In each well, the groundwater surface will be inspected for the presence of separate <br /> phase hydrocarbons(SPHs). Groundwater samples will not be obtained from wells with SPHs. <br /> Groundwater sampling will be performed in accordance with Radian protocols. All <br /> information gathered during sampling will be recorded on a Groundwater Sampling Log (shown in <br /> Appendix A). Groundwater samples will be poured into laboratory-prepared containers, <br /> immediately placed in an insulated ice chest containing crushed ice for temporary storage, and <br /> transported to the laboratory. Samples will be handled in accordance with appropriate chain-of- <br /> custody procedures. <br /> QA/QC samples will be obtained during groundwater sampling. The types of <br /> QA/QC samples will include field duplicates (at the rate of 5% of the total number of <br /> groundwater samples; i.e., one duplicate sample per twenty groundwater samples) and field <br /> equipment blanks (only when nondisposable purging and/or sampling equipment is used). The <br /> field equipment blanks will be obtained on a daily basis during sampling. <br /> Preliminary Site Investigation Work Plan-Final July 9, 1998 <br /> Roberts Property(Former Vernalis Pump Station) <br /> Vernalis,California <br /> 13 <br />