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Kennedy/Jenks Consultants (3) At the beginning of purging and periodically thereafter, record the following information and water quality parameters/observations on the groundwater purge and sample form: As guidance, field parameters may be measured after one purge volume is removed and every % purge volume thereafter. - Date and time - Purge volume and/or flow rate - Water depth - Temperature - pH - Specific conductance - Dissolved oxygen - Oxidation-reduction potential (ORP) - Other observations as appropriate (turbidity, color, presence of odors, sheen, etc.). (4) Continue purging until water quality parameters have stabilized (refer to "Stabilization Criteria for Adequacy of Monitoring Well Purging" below) and/or a minimum of three wetted-casing volumes of water have been removed from the well. If a well purges dry, let it recover to 80 percent of original water column, then sample. If the well takes a very long time to recover(i.e., longer than 2 hours), try to sample the well at the end of day or first thing the next day. (5) Collect the sample in pre-cleaned sample containers suitable for the laboratory analyses to be performed. (6) If sampling using a bailer, use a bottom-emptying device or other technique to avoid sample agitation. If the collected water is very turbid, or a bottom-emptying bailer is not used, properly transfer the water from the bailer into the appropriate sample containers. Be careful to avoid agitating the sample. When sampling for VOCs, turn the bottle upside down after filling the container to identify possible headspace. If bubbles are present, top off the sample container or resample. b. Low-flow purging and sampling. (1) Place the pump intake at a depth equal to the approximate middle or just slightly above the middle of the well screen interval or water column or otherwise as dictated by well- specific soil stratigraphy and project-specific requirements. For example, it may be appropriate that the pump intake be set opposite to any preferential flow pathways (i.e., zones of higher permeability). (2) Place an electronic water-level indicator probe in the well, approximately 0.5 to 3 inches below the piezometric surface. If available, a transducer of sufficient accuracy can also be used to measure depth to water when purging. (3) Connect the pump discharge tube to a flow-through cell housing a water quality parameter probe. (4) Activate the pump for purging at a flow rate ranging from approximately 0.1 to 0.5 liters per minute (L/min) or other flow rate as dictated by project-specific and/or site-specific requirements. (Note: Some regulatory agencies may require specific flow rates). Determine the flow rate by timing the rate at which the flow-through cell is filled. Monitoring Well Installation Work Plan, D-4 Barrel Ten Quarter Circle Land Company, Escalon, California \\SFO\Groups\I S-Group\Admi n1J ob\03\0301 18.27_BTOC LC\09-Reports\M W-Install-WPI n1Appendix\APP_D.doc