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r , ENVIRONMENTAL OVERSIGHT, INC. CONSULTING AND WELL MONITORING SERVICES Ground Water Monitoring Wells FIELD METHODS AND SAMPLING TECHNIQUES Proper sampling techniques must be followed to assure that samples represent actual field conditions and that samples are labeled,preserved, and transported properly to retain sample integrity Tins exhibit describes procedures to be followed by Environmental Oversight,Inc (EOI)during collection of samples of ground water Sampling guidance documents from the American Society of Testing and Materials (ASTM),U S Environmental Protection Agency(EPA), California Department of Health Services(DHS) and the California State Water Resources Control Board will be followed for all sampling procedures Actual sampling procedures to be employed will be based on field conditions and may differ from those described herein Water Level and LPH Thickness Measurements The static water level and LPH thickness in each well will be measured prior to purging or sampling The depth to water/product will be measured using an electronic interface probe The wire of the interface probe is marked at 0 01 foot intervals One tone is emitted from the interface probe if LPH is encountered another tone for water The wire of the interface probe will be lowered slowly until LPH or water is encountered At this point, the mark on the interface wire opposite the permanent reference point on the top of the well casing, or the north side if a mark is not present,will be read to the nearest 0 01 foot and recorded If the first encountered substance is LPH, the probe will be lowered until the tone corresponding to water is emitted This depth will also be recorded the difference between the two depths corresponds to the LPH tluckness The interface probe will be cleaned with an Alconox solution and rinsed in dmomzed water between measurements in different wells Well Evacuation After the static water level in a well is determined and prior to collection of a ground water sample, stagnant water will be removed form the well casing and the surrounding gravel pack by bailing pumping, or with a vacuum truck,utilizing dedicated or decontaminated equipment At least three casing volumes of water will be removed form each well from which a sample is collected. The volume of water in the casing will be determined from the known elevation of the water surface, the well bottom elevation, and the well diameter If the well is bailed or pumped during purging,samples will be collected and field analyzed for pH, temperature,and specific conductance All purged water will be containerized and properly handled and documented for disposal If the containers are stored on site, a label specifying the date of purging, source,and the known or suspected nature of the contents will be affixed to each container lE I E e' E `� •N II E f E I` E