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,. <br /> Quarterly Ground-Water Monitoring October 19, 1989 <br /> Beacon Station No. 492, Manteca, California AGS 86102-4 <br /> FIELD PROCEDURES <br /> Subjective Analysis of,Monitori ells <br /> Ground-water samples are collected for subjective analysis from just below the air-fluid <br /> interface in a monitoring well by lowering approximately half the Iength of a clean Teflon <br /> bailer through the interface. The bailer is retrieved and the water sample examined for <br /> r� floating product, sheen, or other subjective evidence of hydrocarbon contamination. <br /> Measurement of the Iae th to round Wafer i, Monitorine Wells <br /> r) 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 /> 3 <br /> 3 <br /> Pur in and Samaing oL.Maniforing Well <br /> Before sample collection,a minimum of 4 casing volumes of ground water are 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 groundwater sample is collected by <br /> lowering a clean Teflon bailer past the airwater interface. The bailer is retrieved and the <br /> ,a sample is slowly transferred to laboratory-cleaned 40-milliliter glass vials which contain <br /> concentrated hydrochloric acid as a preservative. The vials are completely filed +.hereby <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 /> identification identification number is W-d-MWx where <br /> cation number. The format of the <br /> W r 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 t.Ne date sampled. This record w+'l accompany the samples to the analytical <br /> laboratory. <br /> �' APPIled G"e©SYSMems <br />