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2.4.1 MONITORING WELL DESTRUCTION BY OVER-DRILLING Per San Joaquin Well Standard requirements, wells located in an area of known or suspected contamination or that have laboratory data from the last sampling event that demonstrate the presence of any contaminants of concern are to destroyed by removing all the contents of.the well. Wells MW-2, MW.3, MW-4, MW-5, MW-7, MW-8, MW-9; MW-13-50, MW-14-77, MW- 3 16-50,MW-16-77, MW-16-90, and MW-17-50 meet this criteria. For these wells, the well vaults will be removed, and the upper five feet of each location t will be cleared for.utilities using a vacuumatruck assisted airknife. The wells will then be, drilled out to their original depths using the same size auger originally utilized to install the well (see boring logs Appendix A). The resulting boreholes will be backfilled with neat cement grout through the augers from the_bottom _upward to the depth-of approximately 1 foot below grade (fbg). The upper 1 foot will be filled with concrete or asphalt to match the"surrounding grade. �- - 2.4.2 MONITORING WELL DESTRUCTION BY PRESSURE GROUTING Per San Joaquin Well Standard requirements, wells that have laboratory data from the last sampling event that report non-detectable concentrations of contaminants of concern and with acceptable laboratory detection limits and are not in areas of known of suspected soil contamination, may be destroyed by pressure grouting from the bottom upward,:while leaving the well in placr7MW43-77, ' 01 1 Wells MW-1, MW-6, MW-10, MW-11 W-14-50, and MW-15=77 meet this criteria. o i For these wells the well boxes will be removed; the top three .feet of the well and surrounding soils.to at least one foot larger_in diameter than the original borehole win be'removed using a vacuum truck assisted airknife, and the.casing will be cut off to the depth of;approximately 2.5 fbg:--Cement grout will be added to the well casing from the bottom up usinga tremie pipe until no additional grout will be accepted, and then 25 pounds per square inch of pressure will be applied to the casing for 5 minutes. The grout sealant will then be topped up and'shall spill out of the top of the well casing to form a mushroom cap seal with at least a 1 foot layer of neat cement grout poured six 240778(19) 2 CONESTOGA-ROVERS&ASSOCIATES