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• Field Methods and Procedures Enclosure D <br /> Page 3 <br /> B.5 Soil Sample Screening <br /> After the vapors in the soil samples are allowed to equilibrate with the air in the headspace of the plastic <br /> bags,the organic vapors within the headspace will be screened with a PID or flame ionization detector <br /> equipped with a 10.6 eV lamp calibrated to hexane. The sample bag will be opened and the detector <br /> probe immediately placed within the headspace of the bag. The highest observed reading will be <br /> recorded. This number provides a relative comparison of the petroleum hydrocarbon concentration with <br /> the soil samples but is not quantitative. The field readings will be recorded on the boring logs. <br /> C. WELL CONSTRUCTION <br /> • CA Monitoring Well Filter Pack and Slot Size Selection <br /> The filter pack material of each well will be selected to permit the development of a zone of higher <br /> hydraulic conductivity adjacent to the well screen, but not allow piping of the finer-grained formation <br /> materials into the well. The slot size of the monitoring well screen will be selected such that it will <br /> retain a minimum of 95 percent of the filter pack material. <br /> • C.2 Monitoring Well Development <br /> After the monitoring wells are installed, each well will be developed either prior to emplacement of the <br /> bentonite seal and cement grout, or after a period of 72 hours to allow the grout seals to cure. <br /> Development will be performed using a surge block and submersible pump until the water produced will <br /> be relatively sediment-free. All water produced from the wells during development will be placed in <br /> • drums on site for later disposal. <br /> C.3 Surveying of Wells <br /> California licensed land surveyor,will survey the elevation of each newly installed monitoring well and <br /> the ground surface immediately adjacent to the well.To comply with State of California Assembly Bill <br /> • AB2886, the surveyor will reference the location of the newly installed wells to the California State <br /> Coordinate System using Global Positioning Satellite (GPS) surveying. The top-of-casing (TOC) <br /> elevation of the monitoring wells and ground surface elevation will be surveyed relative to mean sea <br /> level within 0.01-foot. <br /> • D. GROUNDWATER SAMPLING PROCEDURES <br /> The following will describe the procedures for collecting depth to groundwater measurements, <br /> purging and sampling groundwater from monitoring wells. <br /> D.1 Groundwater Sampling <br /> • Each newly installed monitoring well at the site will be purged using a submersible pump until at least <br /> four well casing volumes of water are removed or the well is pumped dry. Wells that are pumped dry will <br /> be allowed to recover to approximately 80 percent of the static water level prior to sampling. After <br /> purging,a water sample will be collected from each well with a clean disposable bailer. Each sample will <br /> be appropriately labeled and stored on ice from the time of collection through the time of delivery to the <br /> • laboratory. Groundwater samples will be transported to the laboratory and analyzed within the <br /> EPA-specified holding times for the requested analyses. <br /> • <br />