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02 October 2023 AdvancedGeo <br /> Project No. 14-3009 An <br /> Employee-Owned Company <br /> Page 2 of 3 <br /> Prior to well destruction activities, all wells will be checked for total depth and well integrity <br /> using a Solinst water level meter. Any obstructions found in the wells will be removed. <br /> Monitoring wells MW-1 through MW-12 are each single-completed with 2-inch diameter <br /> polyvinylchloride (PVC) casing in 8-inch diameter boreholes. All ozone sparge wells are <br /> single-completed with 3/4-inch diameter PVC casing in 8-inch diameter borehole. The two <br /> soil-vapor extraction wells are single-completed with 4-inch well casing installed in 10- <br /> inch boreholes, while the two soi-vapor wells are installed with '/4-inch tubing in 4-inch <br /> boreholes. <br /> AGI proposes to destroy all wells utilizing over-drilling techniques. The wells will be drilled <br /> out to the total depth of each well utilizing a hollow-stem auger drill rig equipped with <br /> either 6-inch, 8-inch or 10-inch diameter hollow stem augers. All original well construction <br /> materials will be completely removed (including well casing, screen, filter pack, and <br /> annular seal) by the drill rig to ensure that no residual contamination is sealed within the <br /> abandoned borehole and a vertical conduit does not remain. <br /> All twenty nine destroyed wells will be completely backfilled to surface grade with a <br /> cement grout mixture (Portland type II) and covered with either concrete or asphalt, <br /> depending on the surrounding surface material. The grout mixture will consist of a ratio <br /> of six gallons water for every 94-pound sack of Portland type II cement. The drill rig hollow <br /> stem augers will be utilized as a tremie pipe for installation of the grout seal. <br /> Rinseate generated during drilling and decontamination activities will be containerized in <br /> properly labeled Department of Transportation (D.O.T.)-approved 55-gallon drums and <br /> stored on-site until proper disposal is arranged to a suitable non-hazardous waste facility. <br /> Additionally, soil cuttings, well materials and construction waste will be containerized in <br /> 20-yard soil bins until proper disposal is arranged to a suitable non-hazardous waste <br /> facility. <br /> 3.0. REPORTING <br /> Upon completion of field work and disposal of waste, a well destruction report describing <br /> the activities and procedures, including documentation of waste disposal, will be <br /> prepared, and submitted to the SJCEHD and CVRWQCB. The report will be in a format <br /> acceptable to the SJCEHD and the CVRWQCB and will be reviewed and signed by a <br /> California Professional Geologist. <br /> If you have any questions or require further information, please contact our office at <br /> (800) 511-9300. <br /> Sincerely, <br />