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Y <br /> n <br /> 4 <br /> I <br /> Quarterly Ground-Water Monitoring <br /> Beacon Station No. 492, Manteca, California January 8, 1990 <br /> � AGS 86102-4 <br /> FIELD PROCEDURES <br /> ® , ub'ective A al sis o Monitorin ells <br /> Groundwater samples .are collected for subjective analysis from just below the air-fluid <br /> interface in a monitoring well by lowering approximately half the length of a clean Teflon <br /> bailer through the interface. The bailer is retrieved and the water sample examined for <br /> floating product, sheen, or other subjective evidence of hydrocarbon contamination. <br /> ease eme t o the evt to Groisnd Water i AX-nitoriaLFells <br /> The depth of the groundwater 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 /> Pu i and am lin of Monitorin Wells <br /> Before sample collection.,a minimum of 4 casing volumes ofrou <br /> each monitoring well,using an electric submersible um g rd water are purged from <br /> e 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-milliliterglass vials that contain <br /> concentrated hydroc,�loric acid as a preservative. The vials are filled completely, 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 /> identification number. The format of the identification number is W-d-MWx, where <br /> .� W = water <br /> F: d depth in feet <br /> € MWx monitoring-well number. <br /> The samples are stored in an insulatedchest with ire to insure preservation. The field <br /> <' geologist initiates a Chain of Custody Record listing each sample number, the site <br /> identification number, and the date sampled. This record will accompany the samples to <br /> z <br /> the analytical laboratory. <br /> 3 <br /> .4,ov�lea' GeoSy�te�e <br />