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Section 2. Standard Operating Procedure <br /> The minimal aeration method described herein has been adapted from the protocols <br /> specified by EPA in their most recent groundwater monitoring guidance (EPA, 1992), <br /> and demonstrated by Barcelona for providing consistent monitoring results for volatile <br /> constituents (Barcelona, 1994). The method is illustrated in Figure 1, and described <br /> below. <br /> 2.1 Equipment Requirements <br /> Equipment needed for sample collection are provided in the attached checklist <br /> (Attachment A). <br /> 2.2 General Pre-Sampling Procedure <br /> Prior to purging and groundwater sampling, the routine procedures listed in the attached <br /> check list(Attachment B) should be conducted. <br /> 2.3 Monitoring Well Purging <br /> The objective of purging the monitoring well is to collect groundwater samples <br /> representative of the formation groundwater. At most petroleum hydrocarbon sites, the <br /> groundwater near the water table surface will have the highest constituent concentrations, <br /> and monitoring wells are therefore screened across the water table. In these wells, the <br /> pump intake should be placed approximately 1 foot below the water level. If the well has <br /> a discreet screen length that is entirely submerged, the pump intake should be placed <br /> within the screened interval approximately 1 foot below the top of the screen. <br /> To collect intrinsic bioremediation parameter samples, monitoring wells should be purged <br /> at a rate that does not lower the water level significantly (i.e., less than 10 percent of the <br /> screen length). The purging rate should be controlled as needed using the pump's <br /> variable speed flow controller and/or the gate valve in the discharge line. Collect water <br /> level measurements frequently during purging to ensure that the water level has not <br /> dropped lower than desired. Monitoring wells should be purged until the field parameters <br /> have stabilized to within the ranges presented in Table 1. If an electric submersible pump <br /> is used, temperature may increase rather than stabilize during low flow rate purging. <br /> SF010030987.DOC D-2 <br />