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