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Quarterly Ground-Water Monitoring October 25, 1989 <br /> Beacon Station No. 502, Lodi. California AGS 86091-7 <br /> FIELD PROCEDURES <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 retrieved and the water sample examined for floating <br /> product, sheen, or other subjective evidence of hydrocarbon contamination. <br /> Measure e t of the De th to Ground Water i MonitoringWells <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 /> Purging and Sampling of MonitorinizWells <br /> Before sample collection, a minimum of 4 casing volumes of ground-water is purged from <br /> each monitoring well using an electric submersible pump. The volume must be sufficient <br /> to produce stable temperature, pH, and conductivity measurements on field instruments. <br /> ., After the well is allowed to recover to static levels, a ground-water sample is collected by <br /> lowering a clean Teflon bailer past the air-water interface. The bailer is retrieved and the <br /> sample is slowly transferred to laboratory-cleaned 40-milliliter glass vials which contain <br /> concentrated hydrochloric acid as a preservative_ The vials are completely filled thereby <br /> eliminating headspace. Labels are affixed to the vials which show the site identification <br /> number, the date and time of sample collection, the preservative used, and the sample <br /> CO identification number. The format of the identification number is: <br /> W-d-MWx W = water <br /> d = depth in feet <br /> MWx = monitoring well number. <br /> The samples are stored in an ice chest with ice to insure preservation. The field geologist <br /> initiates a Chain of Custody Record listing each sample number, the site identification <br /> number, and the date sampled. This record will accompany the samples to the analytical <br /> laboratory. <br /> �° A,ap/led GOOS��t yrs — <br />