SITE INFORMATION AND CORRESPONDENCE_1997

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OCT 16'97 17:40 FR LEVINE F W E 510 6524906 TO 1209 683433 P.03/e6 L •Mari--TSI Tsa • a In an effort to ascertain the best way to abandon well MW-21, we discussed different approaches with two experienced drilling companies(All Terrain Exploration Drilling and Weeps Drilling and Pump Company). Based on these discussions, we believe that the best possible method for well abandonment is to overdrill MW-21,using "drillover pipe." This mud-rotary drilling method utilizes a large diameter, flush-threaded steel pipe with a hollow bit attached. The steel pipe fits over the diameter of the existing well casing, and the existing steel well casing(with a steel cable anchored inside)is used as a guide to keep the drillover pipe centered.The drilling tined circulates down the inside of the drillover pipe and conveys the cuttings to the surface on the outside of the In drillover pipe. Once the bottom of the steel well casing is reached, the steel well casing is removed from the inside of the drillover pipe, using the steel cable. After removing the well casing, the drillover pipe is removed and the borehole is overdrilled using conventional mud- rotary drilling methods. A tricone bit with centralizers(long, heavy, drill rods of nearly the same diameter as the tricone bit)will be used to overdrill the well to a total depth of 149 feet bgs. b t SCS The specific sequence of procedures for abandonment of MW-21 is presented below. 1. Anchor a Sri-inch cable at the base of the MW-21 casing, using concrete, to facilitate casing C p cNcnhro removal. (( . 1y 2. overdrill the existing 5-inch-diameter well casing with an approximately 10-inch-diameter steel drillover pipe equipped with a hollow bit, using mud-rotary drilling methods. 3 P V Q 3. Drill to the base of the MW-21 well casing(117 feet bgs).. GCtw 4. Remove the well casing from the borehole,by cutting it.into approximately 20-foot pieces at the ground surface as the casing is lifted by the X inch steel cable. PV{ G ' 5. Remove the drillover pipe from the borehole. 6. Ream the borehole with a 14-inch4 meter(slightly larger than the original borehole diameter) tricone mud-rotary drill bit, using centralizers to keep the bit on center, to a total boring depth of 149 feet bgs. 7. Grout the entire borehole using treat cement via a tremie pipe. 8. Complete the surface of the grouted borehole with a 6-mch cap of asphaltic concrete. 5" We have selected All Terrain Exploration Drilling of Roseville, California to perform this work. All Terrain Exploration Drilling has extensive experience in this type of well abandonment, and D 1F 5 owns and maintains the drill rigs and necessary equipment to complete this job. All Terrain Exploration Drilling Las provided references and a description of related project experience (see attached). Proposed Work Area and Traffic Plan The proposed work area will be very similar to that used to construct well cluster MW-203B-1,2,3 (Figure 1). As indicated in Figure 1, the mud-rotary drill rig, oversized pipe rack, mud shaker, pa cReo� 1: Ill" `b Valu"' LU-M yi MWIJdLi 1-$RLWa `' ,2N &or ly qo'�nnvn2 5„ S}-CG( GwSt (N VP 10tJ UP rt DU-4-1 i Y�