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V%TC ATC Associates tne. 1117 Lone Pahn Avenue, Suite 201 Modesto, California 95351 209-579-2221 fax: 209-579-2225 ASSOCIATES I N C , STANDARD OPERATING PROCEDURE GROUNDWATER MONITOR WELL PURGING AND SAMPLING Prior to purging the well, the static water level will be measured using an electronic interface probe to evaluate the presence of any phase-separated hydrocarbons. The measurement will be obtained from a reference point on the north side of the top of the well casing. Fluid measurements will be recorded to the nearest 0.01-foot. Depth to groundwater will be measured from all site wells on the same day. The total depth of the well will also be recorded . If phase separated hydrocarbons are noted, a measurement of the apparent thickness will be obtained and the well will not be sampled. To prevent cross-contamination, all monitoring equipment that is in contact with groundwater will be washed with Alconox® detergent and rinsed with distilled water prior to use in each well. After the static groundwater level and total depth of the well has been determined, the volume of water in the well will be calculated. Based on this data, if free floating hydrocarbons are not present, a minimum of three well volumes of water will be purged from the well using a 2-inch Grundfos submersible pump or a PVC bailer. Periodic measurements (at approximate 5-gallon intervals) of temperature, pH, and specific electrical conductivity will be collected during purging. When three successive stabilized readings are obtained, the well will be sampled. If the well is low yielding and is pumped or bailed dry, the well will be allowed to recover at least 80% of the static groundwater level. If the well does not recover 80% within a 24-hour time frame, a sample will be collected and recovery noted on the Groundwater Sampling Log. Groundwater purged from the well will be stored on site in 55-gallon drums pending proper disposition. To prevent cross-contamination, equipment will be washed with Alconox® detergent and rinsed with distilled water prior to use in the well. Groundwater samples will be collected from the well using a disposable polyethylene bailer. Each sample will be collected in laboratory-preserved l-liter glass bottles and in 40-milliliter volatile organic analysis (VOA) vials. Each vial will be filled completely with sample and preservatives to eliminate headspace and create a positive meniscus. The vial will be capped with convex Teflon septa. Each vial will be observed to ensure that no air bubbles are present within the vial. Samples will be marked for identification, placed on ice, and transported to a State-certified laboratory for analysis. Chain-of-custody records will be maintained and accompany all samples to the analytical laboratory.