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Flag City Chevron - 2 - 25 March 2008 <br /> 6421 Capitol Ave., Lodi <br /> around the CMT well to anchor the cylinder in the boring, CMT wells are not rigid cased or <br /> cemented in place, and as such, cannot be effectively over-drilled by Hollow Stem Auger (HSA) <br /> as prescribed by SJCEHD well ordinance. The SJCEHD Letter specifically allows one trial <br /> attempt for CMT well MW-10 destruction using a GeoprobeTm drill rod pushed down the entire <br /> depth of the center chamber, to open up the remaining six chambers while staying centered in <br /> the CMT casing, then using a 22-inch auger to excavate the well box to three feet depth, then <br /> recover the CMT casing and, after attaching a grout collar, pressure grouting the entire well. <br /> The Workplan selected CMT well MW-12, which has also been consistently non-detect for <br /> petroleum hydrocarbons. <br /> The SJCEHD has verbally agreed to allow an alternate CMT well decommissioning method, if <br /> the push and grout method proves ineffective. The alternative method proposed in the <br /> Workplan requires grout be injected into in the outer six chambers of the CMT well. Following <br /> grouting, a line charge explosive would be placed down the center chamber and then <br /> detonated, destroying the soft casing and collapsing native material into the boring. To our <br /> knowledge, neither proposed well decommissioning method has been attempted on CMT wells <br /> in San Joaquin County. <br /> All conventional constructed polyvinyl chloride (PVC) monitoring/remediation wells scheduled <br /> for destruction will be decommissioned by overdrilling the entire casing to total depth using a <br /> HSA drill rig, and then by tremie grouting the boring. <br /> Four conventionally constructed monitoring wells (MW-19A and —19B, MW-20A and -20B) will <br /> be transferred from Flag City Chevron to the New West Petroleum for their site investigation <br /> and, when authorized by Regional Board staff, will be properly decommissioned by New West <br /> Petroleum. <br /> The Workplan concludes that a report will include a description of the activities, disposal of all <br /> wastes, and a section for conclusions/recommendations, if applicable. <br /> Comments: The Workplan is conditionally approved with the following modifications: <br /> 1. Regional Board and SJCEHD staffs discussed the Workplan on 19 March 2008. We are <br /> concerned that the attempt to push the drill rod down the center chamber or auger out <br /> the surface completion might result in a blocked passageway in the CMT tubing so that <br /> MW-12 cannot be pressure grouted the entire length of the well If the CMT well <br /> becomes blocked near the surface, then there remains the possibility that a small conduit <br /> may open to allow communication between aquifers in the remainder of the ungrouted <br /> CMT well as the plastic well casing deteriorates with time. Another concern is that the <br /> rigid drill rod may wander off the center and puncture the outside of the CMT casing due <br /> to the effect of "corkscrewing" of the boring prior to installing the CMT wells, which could <br /> effectively short circuit the push method. To reduce the risk, we require that, prior to <br /> attempting the push and pressure grouting well destruction(s), the outer CMT chambers <br /> should be grouted up to the top of each chamber. <br /> 2. If refusal occurs before total depth of the well is reached, then the well will be tremie <br /> grouted after the rod is removed. The depth to the well obstruction will be recorded in <br />