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Water Sample Labeling and Handling <br /> Sample containers are labeled in the field with the job number, sample location, depth of <br /> sample (if appropriate), and date of sample and promptly placed in iced storage for transport to <br /> the laboratory. A Chain of Custody Record is initiated by the geologist and updated <br /> throughout handling of the samples and accompanies the samples to a laboratory certified by <br /> the State of California. Samples are transported to the laboratory promptly to help ensure that <br /> recommended sample holding times are not exceeded. <br /> Reporting Results of Analyses <br /> Hydrocarbon constituents in soil samples are typically reported in units of parts per million <br /> (ppm). Hydrocarbon constituents in groundwater samples are typically reported by the <br /> laboratory in units of parts per billion (ppb). <br /> Evaluating the Groundwater Flow Direction and Gradient <br /> The elevations and positions ("x" and "y" lateral coordinates) of the monitoring well are <br /> surveyed with respect to a local datum that references the elevation according to mean sea <br /> level. The elevation of the monitoring wells are measured within 0.01 foot of the local datum. <br /> The horizontal distances are measured to the nearest 0.1 foot. The elevations are typically <br /> measured from either a notch or an arrow marked on the top northern edge of the well casing. <br /> The groundwater elevation for each monitoring well is calculated by subtracting the depth to <br /> water from the wellhead elevation. The groundwater elevation information is used to construct <br /> a potentiometric surface map, which is used to evaluate the direction of groundwater flow and <br /> the magnitude of the groundwater gradient. <br /> SHELLS\FLDMTHDS.doc 4 <br />