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Sampling of Ground-Water Monitoring Wells Septembzr 4, 1990 <br /> Beacon Station No. 502, Lodi, California AGS 86091-8 <br /> FIELD PROCEDURES <br /> Measuret.,nent of the Flsath to Ground Water in onitorin ells <br /> The depth of the ground-water surface in a monitoring well is measured from the top of the <br /> well casing to the nearest 0.01 foot with a Solinst water-level indicator. <br /> Subiective Analysis of Ground-Water <br /> Ground-water sarples are collected for subjective analysis from the air-fluid interface in a <br /> monitoring well by lowering approximately half the length of a clean Teflon bailer through <br /> the interface. The bailer is retrieved and the water sample is visually 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 ground water is purged from <br /> . ::bmersible pump. A sufficient volume is purged to <br /> each monitoring well using an electric s <br /> uctivity of the water to stabilize. After the water level in <br /> allow temperature, pH, and cond <br /> the well is allowed to recover to at least 80 percent of the initial level, a ground-water <br /> sample is collected by lowering a clean Teflon bailer past the air-water interface. The bailer <br /> is retrieved and the sample is slowly transferred to laboratory-cleaned, 40-milliliter glass <br /> vials that contain concentrated hydrochloric acid as a preservative. The vials a:a completely <br /> filled so as to prevent headspace. The vials are labeled with the site identification number, <br /> the date and time of sample collection,the preservative used,and the sample identification <br /> number. The samples are promptly placed in iced storage and delivered to a laboratory <br /> certified by the State of California. <br /> , <br /> `--A,tap1Ee0' GoOSYStems <br />