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• •Hi Charlie, I think we can resolve this without a conference call today. The changes to the well installation approach need to be reviewed by San Joaquin County for their drilling permit. Please contact them and let me know that they agree to the 10" temporary conductor casing to 70 ft. bgs and 6" telescoping drive casing to 90 ft bgs. As to moving the wells a few feet to avoid the sidewalk and possible utilities, that is always an option for the responsible professional when conditions in the field necessitate a change. Screening wells in more permeable zones is also approved if logs show that the proposed depths will miss potential migration pathways. However the revised Figure 9A (attached) shows that the wells will be at least 7 feet from the back of curb, which appear to be out of the sidewalk. At this point since your geologist requested the changes after a site visit, I am inclined to concur to a two or three (few) feet change in location if it is documented in the report with the reasons for the change and an updated Figure for the well locations. The workplan discusses utilities clearance before initiating any borings, and references the Shaw well installation SOP. Neither the workplan nor the SOP address how Shaw plans to start the borings (air knife or hand auger to an approved depth) to reduce the risk of accidental impacts to utilities. Please provide San Joaquin County and myself with an email response of the method Shaw will employ to reduce the risk to utilities when starting the borings. Thanks. Jim Barton James L.L. Barton, P.G. Engineering Geologist California Regional Water Quality Control Board Central Valley Region, 11020 Sun Center Drive, Suite 200, Rancho Cordova, CA 95670 office (916) 464-4615 fax (916) 464-4704 >>> "So, Charlie" <Charlie.So@shawgrp.com> 2/11/2008 11:17:58 AM >>> Hi Jim, The primary proposed change has to do with the installation approach for the deep wells. As described in Section 4.2.2 of the Work Plan, the deep boring will be drilled to a total depth of 90 feet bgs through the use of air rotary techniques. The initial 75 feet of boring will be bored via air rotary and isolated through the advancement of steel conductive casing as the boring is conducted. Twelve-inch diameter steel casing will be first advanced to a total depth of 75 feet bgs with air rotary opening the borehole to the same depth. An approximate 9-inch diameter steel conductive casing will then be installed within the 12-inch diameter casing. The annular space between the two casings, and within the 9-inch diameter conductive casing will be grouted to surface. The grouted casings will be allowed to set for 24 hours prior to continued drilling. Air rotary drilling will then be conducted through the inner 9-inch diameter casing and continued to a maximum depth of 90 feet bgs. The proposed new approach will continue to use air rotary techniques to drive nominal 10- inch temporary conductor casing but to 70 feet bgs and then telescope nominal 6-inch drive casing to 90 feet bgs. No permanent casing will be required. The 2-inch well will then be constructed within the nominal 6-inch casing as described in the Work Plan. Both the lower and upper conductor casings will be withdrawn and grouted in one operation. This revised well installation method will still ensure the prevention of vertical cross contamination. The proposed change is considered necessary to facilitate the timely and efficient installation of the deep wells at the site that has very limited work space available. The space restrictions noted from the visual inspection of the site conditions last Thursday (2/7) basically helped determine the more feasible drilling method at the site. Along with a similar subject, we would like to inquire about RWQCB's position on 2