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GROUND ZERO ANALYSIS, INC. ,Q? 7 38 1714 Main Street Escalon, California 95320-1927 Telephone: (209)838-9888 Facsimile: (209)838-9883 August 9, 2001 Mr. Harlin Knoll San Joaquin County Public Health Services Environmental Health Division 304 East Weber Avenue, Third Floor Stockton, CA 95202 Subject: Workplan for Abandonment of Wells MW6 through MW8 1 140 W. Hammer Lane, Stockton, California (Figure 1) Dear Mr. Knoll: As we discussed Ground Zero Analysis, Inc. (Ground Zero) is submitting this workplan on behalf of Mr. Carl Knowles to abandon groundwater monitoring wells at the subject site. As recommended in our June 28, 2001 Feasibility Study Report, Ground Zero proposes to destroy wells MW6 and MW7 by pressure grouting. Also as we discussed, Ground Zero is proposing to destroy well MW8 by pressure grouting based upon historical analytical results. Well MW8 is located within the footpring of the proposed road widening project along that stretch of Thornton Road. Monitoring well locations are shown on Figure 2. Monitoring well construction details are presented in Table 1. Copies of well logs are included in Attachment A. Prior to abandonment, each well will be monitored to ensure no obstructions are present. To abandon the wells neat cement grout will pumped continuously into each respective well until completely full, unless conditions in the well(s) dictate that sealing operations be conducted in a staged manner. Additional cement will then be added to each well under pressure in order to force the grout through the slots of the screen and into the filterpack, ensuring an adequate seal. Pressure will be applied to each well for a minimum of 15 minutes after completely filling the well with cement grout. The well boxes and upper well casing will be removed to at least 18 inches. Grout used to seal the wells will be allowed to spill over into the respective voids and finished to grade. G:\Data\GRO[TNDZE\KNOWLES.HAM\REPORTS\W ELLDST.doc