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a / Page 3 Ground water samples will be removed from the monitoring well only after a minimum of five (5) casing volumes have been purged from the well casing, and purging has been of sufficient duration to result in the stabilization of pH, temperature, and EC readings. A well purging/sampling log will be maintained for purging of each monitoring well. The field parameters of pH, temperature, and EC parameters will be monitored and recorded during the purging operations at a minimum rate of two (2) readings per casing volume purged. Stabilization of the parameters of pH, temperature and EC will be used to indicate that the well has been sufficiently purged for sampling. Parameter stabilization will be indicated by at least three near- constant pH, temperature, and EC values for a minimum of one (1) casing volume. The acceptable range of values for stabilization of the field parameters are ±0. 5°C for temperature, ±0. 2 for pH, and ±10 percent of the total value of EC. Standardization of field equipment will be done at the beginning of each use, according to manufactures ' specifications and consistent with methods described in EPA SW-846, Test Methods for Evaluating Solid Waste Physical/Chemical Methods. . Sample Collection Samples of non-stagnant formation water will be collected only after the minimum of five (5) casing volumes of water have been purged from the casing and field parameters have stabilized. In low yield formation wells which were purged to dryness, the sample (s) will be collected as soon as the well has recovered sufficiently for sample collection. All samples will be collected in an order such that those para- meters most sensitive to volatization will be sampled first. A general order of collection for some common ground water parameters follows: - Volatile Organics Compounds (VOC' s) - Total Organic Halogens (TOX) - Total Organic Carbon (TOC) - Total Metals -- Dissolved Metals - Phenols - Sulfate and Chloride