WORK PLANS - Laserfiche WebLink

Home Browse Search

Mr. Gil Moore • July 13, 2012 6437 Banner Street, Lodi Page 2 of 3 Well Destruction Work Plan review additional technical justifications later provided by AGE on 14 May 2012 to support the proposal for pressure grouting most of the fourteen wells. To summarize, the AGE technical justifications supplied to EHD were based on traffic safety concerns, convenience of local businesses and fire station, and contaminant concentration decline trends or inferences of lack of contamination derived from nearby wells. EHD investigated and evaluated all these issues and found the following: ® Any active traffic creates some risk of injury to workers in the area; however, EHD visited the site and found that unusually heavy or fast traffic conditions were not observed and visibility appeared to be good along the roadway. No safety concerns were found that could not be mitigated by proper traffic control methods commonly used by well contractors and consultants who routinely install and destroy monitoring wells at this type of site. • An interview conducted with the officer of the fire station found that the station could easily take steps to accommodate the presence of a drill rig for destroying the wells in its area, all the while still being able to provide the level of response required during incidents of fire. ® The local businesses should not be inconvenienced any more in the process to destroy the wells than when the wells were constructed. ® The declining concentration trends were developed from data collected during active remediation and are not likely to represent the contaminant degradation rate under natural_conditions ® The contaminant concentrations in the wells compared to one another when sampled at the same time displayed a poor correlation between wells, so one well could not be reliably used to predict the contaminant concentrations in the nearby well. As such, the EHD has determined that the fourteen wells must still be destroyed by removing the well contents. The AGE well destruction proposal for the fourteen wells submitted to EHD on 11 June 2012 has been reviewed. The proposal, which the consultant referred to as the `popsicle' method, involves pulling the well casings from the borehole and grouting the remaining open bore hole through the casing during its removal. In instances where the casing cannot be successfully removed, it is proposed that the well then be pressure grouted and over-drilled to the saturated zone and finished by grouting the remaining open borehole to surface grade. This procedure would not meet destruction requirements of Section 13.17.6 and several elements of this method are of concern: 6 If the well casing can be successfully removed, but only a portion or none of the cement grout seal pulls out with it, the residual annular grout seal will be adjacent to the grout introduced to seal the open hole. Well Standard Section 13.17.9., requires that "Sealing materials shall be placed in one continuous operation unless conditions in the well or boring dictate that sealing operations be conducted in a staged manner and prior approval is obtained from the Director." When repairing broken cement with new cement, the new often does not adhere well to the older cement, thus a vertical space may be left