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i San Joaquin County Environmental Health Department RE: Beneto, Inc., 749 E. Charter Way, Stockton, CA Page 2 of 4 equipment and conductor casing will be set across the potentially contaminated upper aquifer zone(s). Well MWI7B will be completed with a screened interval from approximately 85-95 feet bgs and well MW18C will be completed with a screened interval from approximately 130- 140 feet bgs, based upon the results of the CPT investigation conducted in July 2005 . A copy of the CPT log (boring B-4) from the previous investigation is included in Attachment 1 . Drilling and Well Construction MW 17B An 11 '/4-inch diameter boring will be drilled with mud rotary equipment to a depth of approximately 80 feet bgs at which point a clay bed should be present. Drilling mud will be kept in a slightly overbalanced condition in order to minimize fluid en g y try into the well bore. 6 5/s inch Dv Z5 1 7 diameter welded steel conductor casing led by a grouting shoe will be set in the clay bed for grouting. Three equally spaced centralizers will be installed on the casing to ensure a uniform thickness of annular seal and to prevent cement channeling. The conductor casing will be grouted through the shoe with Class II neat cement, which will be circulated through the annulus to the surface and allowed to cure for a period of approximately 48-72 hours . After the cement has cured, the grout shoe will be drilled out and a 6-inch diameter boring will be advanced to a depth of approximately 95 feet bgs using mud rotary equipment. Drilling mud will be changed after drilling out the shoe and will be kept in an overbalanced condition to minimize fluid entry and to control possible heaving sands. Ln ` _ To complete the well, 2-inch diameter PVC casing equipped with centralizers and 10 feet of 0.020 slot pre-packed screen will be set from the bottom of the boring, to grade. The screened b ' � interval will be from approximately 85-95 feet bgs. Approximately 2 additional feet of filter pack will be placed above the pre-packed screen. The remaining annulus will be completed with 2 feet of bentonite overlain by neat cement grout to the surface, emplaced with a tremie system. At the surface, the well will be fitted with a locking cap and watertight, traffic rated well box. A well construction diagram for MW 17B is shown on Figure 3 . h MW18C An 11 '/4-inch diameter boring will be drilled with mud rotary equipment to a depth of approximately 115 feet bgs at which point a clay bed should be present. Drilling mud will be kept in a slightly overbalanced condition in order to minimize fluid entry into the well bore. 6 %- inch diameter welded steel conductor casing led by a grouting shoe will be set in the clay bed for grouting. Three equally spaced centralizers will be installed on the casing to ensure a uniform thickness of annular seal and to prevent cement channeling. The conductor casing will be grouted through the shoe with Class II neat cement, which will be circulated through the annulus to the surface and allowed to cure for a period of approximately 48-72 hours. After the cement has cured, the grout shoe will be drilled out and a 6-inch diameter boring will be advanced to a depth of approximately 140 feet bgs using mud rotary equipment. Drilling mud UAL&PTenetoMKPLAN_deepwells.doc