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APPENDIX B Monitoring and Sampling Procedures STALLWORTH AUTO SALES 602 North California Street, Stockton, California STATIC WATER LEVEL MEASUREMENTS Before sampling and during groundwater monitoring, static water levels are measured using an electric water level indicator. Water level data is recorded to the nearest 0.01-foot from a reference point marked on the top of the PVC well casing. WELL EVACUATION Subsequent to measurement of depth to water and prior to sampling, each well is purged to ensure samples are representative of the formation, rather than standing water in the well casing. Wells are purged using a Waterra inertia pump and dedicated 5/8-inch plastic tubing or disposable polyethylene bailers. Wells are purged until a minimum of three casing-water volumes are removed from the well and/or the field-measured ground water parameters (pH, temperature, and conductivity) are stabilized. However, if a well is purged dry prior to evacuating three casing volumes, a sample is collected following 80 percent recovery of ground water within the well, or after a minimum of one hour, but within eight hours, of well evacuation. Field data and logs are provided in Appendix C. SAMPLE WITHDRAWAL Water samples are collected from each monitoring well using an inertia pump with dedicated plastic/Teflon tubing or disposable polyethylene bailers; plastic tubing used with the inertia pump is either dedicated to each well point or changed at each sampling event, thereby minimizing cross contamination due to sampling devices. Samples are drawn and collected in such a manner that agitation and exposure of the groundwater to the atmosphere is minimal. SAMPLE HANDLING Groundwater samples are collected into laboratory-supplied 40-ml volatile organic analysis (VOA) vials without preservative and one 1-liter amber bottle; samples are collected with no visible air bubbles present in the VOAs after filling and capping. Following collection, samples are appropriately labeled, placed on ice, and kept in a cooler until delivered to Cal Tech Environmental Laboratories (CTEL), a State of California Department of Public Advanced GeoEnvironmental,Inc.