SITE INFORMATION AND CORRESPONDENCE

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• page 4 Drilling and sampling procedures characteristics are stable prior to sampling. Stable in this situation is three consecutive readings within 15% of each other. If the wells are emptied before three well volumes are removed, the sample shall be taken when the water level in the well recovers to at least 80% of its initial water level. Samples are then taken immediately after purging using a teflon bailer and transferred into 40 milliliter (ml) glass vials with Teflon septum lids using a collection procedure that precludes air from entering the 40 ml sample vials and prevent the release of volatile organic compounds. To prevent cross-contamination of the ground-water samples, the Teflon bailer is washed with tri-sodium phosphate solution, rinsed with tap water, then distilled water, and allowed to air dry before sampling the next well. The samples are then labeled and placed immediately in a cooler for delivery to a state certified analytical laboratory. A chain of custody shall accompany the samples and contain the information concerning the source of the samples. Field identification of the samples, date and time of sample collection, analyses required, and signatures of the sampler and other handlers. For the purpose of quality assurance, one or more duplicate ground-water samples are taken for each five wells sampled. A sample is taken of distilled water from the final bailer rinse. Trip blanks furnished by the laboratory are also utilized. Additional Ground-Water Parameters Dissolved Oxygen Content The dissolved oxygen content of the ground water is measured with a Yellow Springs Instrument, Model 51B dissolved oxygen meter, or equivalent, which is calibrated on site taking into account temperature and salinity. After purging, a ground water sample is taken with a teflon bailer. The sample is immediately transferred into a jar in a manner that precludes air from being introduced into the sample. The dissolved oxygen probe is than placed in the jar, directly measuring the water temperature and the dissolved oxygen content.