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APPENDIX A <br /> GENERAL FIELD PROCEDURES <br /> Fluid-level Monitoring <br /> Fluid levels are monitored in the wells using an electronic sounder with optical and conductance <br /> sensors. The presence of free product is verified using a hydrocarbon-reactive paste. The depth <br /> of free-product and water is measured relative to the top of the well box. Well box or casing <br /> elevations are surveyed to within 0.002 foot relative to a county or city benchmark. <br /> Ground Water Purging and Sampling P_rqggdures <br /> Typically, all monitoring wells not containing free product are purged of ground water prior to <br /> sampling so that fluids sampled are representative of the formation. Temperature, pH, and <br /> specific conductance are typically measured after one well and annular sand pack volume have <br /> been removed, and after every 112 volume thereafter. Purging is complete when these <br /> parameters vary less than 10%Q from the previous readings or when three borehole volumes of <br /> fluid has been removed. Samples are collected without further purging if the well does not <br /> recharge within 2 hours to 80% of its volume before purging. <br /> All purging equipment that could contact well fluids is either dedicated to a particular well or <br /> cleaned prior to each use in a Liqui-nox solution followed by two tap water rinses. The purged <br /> water is eitherpumped directly into a licensed vacuum truck or temporarily stored in labeled <br /> barrels prior to transport to an appropriate treatment or recycling facility. If an automatic <br /> recovery system {ARS} is present at the site, purged water can be pumped into the ARS for <br /> treatment. <br /> Samples are collected by lowering a 2-inch-diameter bottom-fill Teflon or disposable bailer just <br /> below the well static water level. The sample is carefully transferred from the check-valve- <br /> equipped bailer to 1-liter and 40-milliliter glass containers. These containers are filled to zero <br /> headspace and fitted with Teflon-sealed caps. Each sample is labeled with the project number, <br /> well number, sample date, and the collector's initials. Samples remain chilled at approximately <br /> 4 degrees Celsius until laboratory analysis. <br /> • <br />