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olirr. BEIM <br /> r <br /> s <br /> Fmeasur <br /> ly Ground-Water Monitoring January 22, 1994 <br /> Station No. 492, Manteca, California <br /> AGS 86102.4 <br /> FIELD PROCEDURES <br /> n.ient of the De th to round ater in Manitori elle <br /> The depth of the ground-water surface in a monitoring well is measured frorn the top of <br /> the wed casing to the nearest 0.01 foot with a Solinst water-level indicator. <br /> ® Sub;ective Analysis of Mor�itc�rin`Q�lepls <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, and other subjective evidence of hydrocarbon contamination. <br /> . r <br /> Pur rin and ani fin of Monitor' ells <br /> Before sample collection, a minimum of 4 casing volumes of ground water is purged from <br /> #y each monitorij,g wall 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 slowlk transferred to laboratory-cleaned, 40-milliliter glass vials that contain <br /> concentrated hydrochloric acid as a preservative. The vials are filled so as to prevent <br /> headspace. Labels which show the site identification number,the date and time of sample <br /> collection, the preservative used, and the sample identification number ate affixed to the <br /> .vials. The format of.the identification number is: <br /> W-d-Wx W water <br /> si d = depth in feet <br /> MWx @ monitoring-well number <br /> The samples are promptly stored in an ice chest with ice. The field geologist initiates a <br /> Chain of Custody Record listing each sample number, the site identification number, and <br /> the date sampled. This record will accompany the samples to the analytical laboratory. <br /> •4w,v!!e� �eoSj�tems <br />