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Environmental <br /> Mr Harlin Knoll Resources <br /> 17 February 2000 Management <br /> Page 2 <br /> • <br /> Closure Report - 1325 and 1515 W Weber Avenue - Stockton, California <br /> (ERM, October 1999, hereinafter "Closure Report") <br /> PROPOSED SCOPE OF WORK <br /> As noted above, the scope of work proposed in this Workplan is to <br /> abandon the ten existing monitoring wells at Former Tanks #1 and #2 <br /> Well specifications are presented on Table 1 <br /> The monitoring wells will be abandoned according to state and county <br /> requirements California state requirements for the destruction of <br /> monitoring wells are described in the following documents California <br /> Well Standards Bulletin 74-90, (California Department of Water Resources, <br /> June 1991) and Monitoring Well Design and Construction for Hydrogeologic <br /> Characterization - Guidance Manual for Ground Water Investigations <br /> (California Environmental Protection Agency,July 1995) ERM will <br /> • obtain appropriate permits from the PHS/EHD prior to abandonment <br /> ERM will notify PHS/EHD of the exact schedule one week prior to field <br /> activities <br /> Well Abandonment Procedures <br /> The total depth of each well will first be measured and compared to the <br /> original well specifications to verify that significant silting, bridging or <br /> casing failure has not occurred Based on observations during the recent <br /> ground water monitoring, the wells do not appear to have significant <br /> silting, bridging, or casing failure Therefore, we propose to abandon the <br /> wells using pressure grouting methods The estimated casing volumes <br /> for each well provided in Table 1 indicate the approximate amount of <br /> grout needed for abandonment The grout used will consist of neat <br /> cement Approximately 5 gallons of water will be used per each 94- <br /> pound bag of grout The grout will be pumped into the casing through a <br /> tremmie pipe extending to within 3 feet of the bottom of the casing <br /> While falling the casing, an external pump will be used to create <br /> additional pressure at the well head The external pump will be <br /> plumbed through fittings installed on a pressure resistant cap, which is <br /> installed on the well head Additional external pressure will be <br /> maintained until the well ceases to accept any additional grout Once the <br /> grout is in place, the top 3 feet of casing will be removed by overdrilling <br /> with a hollow-stem auger drill rig Hollow-stem augers (with a diameter <br /> equivalent to or larger than those originally used to drill the well <br />