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APPENDIX B <br /> Monitoring and Sampling Procedures <br /> MAIN STREET INVESTORS (CITY OF STOCKTON) <br /> 601 East Main Street, Stockton, California <br /> STATIC WATER LEVEL MEASUREMENTS <br /> Before sampling and during groundwater monitoring, static water levels will be <br /> measured at all wells using an electric water level indicator. Water level data is recorded <br /> to the nearest 0.01-foot from a reference point marked on the top of the PVC well <br /> casing. <br /> WELL PURGING <br /> Subsequent to measurement of depth to water and prior to sampling, each well is <br /> purged to ensure samples are representative of the formation, rather than standing <br /> water in the well casing. Wells are purged using a Waterra inertial pump and dedicated <br /> %-inch plastic tubing or a disposable polyethylene bailer. <br /> Wells are purged until a minimum of three casing-water volumes are removed from the <br /> well and/or the field-measured groundwater parameters (pH, temperature, and <br /> conductivity) are stabilized. However, if a well is purged dry prior to evacuating three <br /> casing volumes, a sample is collected following 80 percent recovery of groundwater <br /> within the well, or after a minimum of one hour, but within eight hours, of purging <br /> procedures. <br /> SAMPLE WITHDRAWAL <br /> Water samples are collected from each monitoring well using a disposable polyethylene <br /> bailer. Bailers are disposed of after a single use (sample) and require no <br /> decontaminating. Samples are drawn and collected in such a manner that agitation and <br /> exposure of the groundwater to the atmosphere is minimal. <br /> SAMPLE HANDLING <br /> Groundwater samples are collected into laboratory-supplied 40-ml volatile organic <br /> analysis (VOA) vials with preservative and one-liter amber glass containers without a <br /> preservative; the samples are collected with no visible air bubbles present in the vials <br /> after filling and capping. Following collection, samples are appropriately labeled, placed <br /> on ice, and kept in a cooler until delivered to a State of California Environmental <br /> Laboratory Accreditation Program-certified analytical laboratory, for analysis. The <br /> samples are analyzed for: <br />