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Quarterly Ground-`.Water Monitoring May 10, 1990 <br /> Beacon Station No. 502, Lodi, California AGS 86091-7 <br /> FIELD PROCEDURES <br /> a-� <br /> Measurement of the-Depth to Ground Water in.Monitoring Wells <br /> The depth of the ground-water surface in a monitoring well is measured from the top of <br /> the well casing to the nearest 0.01 foot with a Solinst water-level indicator. <br /> Subjective Analysis of Monitoring Wells <br /> Ground-water samples are collected for subjective analysis from the air-fluid interface in <br /> a monitoring well by lowering approximately half the length of a clean Teflon bailer <br /> through the interface. The bailer is rAtrieved and the water sample examined for floating <br /> product, sheen, and other subjective evidence of hydrocarbon contamination. <br /> Purging and Sampling of Monitoring_Wells <br /> Before sample collection, a minimum of 4 well volumes of grot..id water is purged from <br /> each monitoring well using an electric submersible pump. The volume must be sufficient <br /> to allow temperature, pH, and conductivity to stabilize as measured with field instruments. <br /> After the well is allowed to recover to static levels, a ground-water sample is collected by <br /> lowering a clean stainless steel bailer past the air-water interface. The bailer is retrieved <br /> and the sample is slowly transferred to laboratory-cleaned, 40-milliliter glass vials that <br /> contain concentrated hydrochloric acid as a preservative. The vials are filled so as to <br /> 0.6 prevent headspace. The vials are labeled with the site identification number, the date and <br /> time of sample collection, the preservative used, and the sample identification number. <br /> The samples are promptly placed in iced storage for delivery to a laboratory certified by <br /> the State of California. <br />