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December 23, 1999 Pcr,~~e C'-d • C.3.3.1 Preparation for Purging Before well purging begins, the following procedures are to be performed at each well: Note the condition of the outer well casing, concrete well pad, protective posts (if present), and any other unusual conditions of the area around the well. Open the well. Note the condition of the inner well cap and size of outside diameter of casing. Measure (to nearest 0.01 foot) and record depth of static water level from the measuring point on the well casing and indicate time. Record what the measuring point is (i.e., notch on north side, top of PVC well casing). Calculate volume of water in the well casing in gallons based on feet of water in well and casing diameter. (For micropurging, calculate the tubing volume.) C.3.3.2 Purge Volume Cn/culalions The volume of water purged from the well should be adequate to remove all stored water from the well casing prior to sampling. • Two exceptions to this approach may be encountered: wells which are very low-yield or wells which are extremely deep or large diameter. [n low-yielding wells, the casing may be purged dry. This will effectively remove all stored water in the casing, and the sample can be collected when the water level recovers sufficiently to allow for sample collection. Indeep orlarge-diameter wells having a volume so large as to make removal ofall water impractical, micropurge techniques should be employed. If micropurging techniques are employed, then a volume of water equal to two times the combined volume of the tubing and pump should be purged prior to sampling. C.3.4 Groundwater Sample Collection Obtain samples for chemical analysis immediately after purging is completed. For slow recovering wells, the sample will be collected immediately after a sufficient volume of water is available. Most wells are equipped with dedicated equipment, but the water quality samples may be collected using bailers or submersible downhole pumps. The following sampling procedure should be used at each well: Assemble decontaminated sampling equipment. If bailers are used for sampling, a • bailer will be dedicated for each well. Assemble the manual filtering apparatus. Fill out the sample bottle labels and attach to the appropriate sample bodies. Write in all information except the sampling time. Agapito Associates, Inc.