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I VIII. GROUNDWATER SAMPLING ,o Prior to water sampling, a minimum of 24 hours following well development, and after water levels have been allowed to stabilized in the well, each well is purged by the evacuation of between four and ten wetted casing volumes of groundwater. Purging is continued until the water produced is relatively sediment-free and measurements of PH, specific conductance, and temperature stabilize, ten casing volumes have been 1 purged, or the well bails dry. Stabilization is achieved when three successive measurements of each of the three parameters have been recorded that are within 10%. Where required, a turbidity meter is utilized. If the well is bailed dry during the development process, recharge rates will be recorded. When practical, the groundwater sample should be taken when the water level in the well recovers to at least 80% of its static level. No water or chemicals will be introduced into the monitoring wells during well development. All developed water is placed in an appropriate vessel on site for later disposal pursuant to appropriate local and state regulations. The sampling equipment consists of a factory pre-cleaned disposable PVC bailer. Groundwater samples for volatile organic analysis (VOA) are collected in factory pre- cleaned specialized VOA vials with teflon septa. The sample is collected such that no headspace is contained with the VOA vial. The sample is then labeled and the sample identification is written directly on the sample in indelible ink. The sample label includes a unique sample number, well number, location if applicable, date, samplers 11110 initials, and site address. The sample is immediately placed in a cooler with ice or blue ice for transport to a state-certified analytical laboratory, or for relinquishment to on site laboratory personnel. Proper chain-of-custody procedures described in technical approach Quality Assurance quality control are be established and followed. 0 For quality control purposes, a duplicate water sample is collected from each well. This sample is put on hold at the laboratory. When required, a trip blank is prepared at the laboratory and placed in the transport cooler. It is labeled similar to the well samples, remains in the cooler during transport and is analyzed by the laboratory along with the groundwater samples. In addition, a field blank may be prepared in the field 6 when sampling equipment is not dedicated. The field blank is prepared after a bailer has been either steam cleaned or properly washed, prior to use in the next well, and is analyzed along with the other samples. The field blank analysis demonstrates the effectiveness of the in-field cleaning procedures to prevent cross-contamination. To minimize the potential for crass-contamination between wells, all well development and water sampling equipment not dedicated to a well is either steam cleaned or properly washed between use. As a second precautionary measure, wells are sampled in order of least to highest concentrations as established by available previous analyses.