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w CB81 180 Promenade Circle,Suite 320 Sacramento,CA 95834 Telephone:916-565-4316 December 23,2014 Project 149259 Taj M.Bahadori,P.E. Senior Civil Engineer San Joaquin Department of Public Works Solid Waste Division 1810 E.Hazelton Avenue Stockton,CA 95201 Re: Revised Work Plan for Proposed Monitoring Well MW-6 at the Foothill Sanitary Landfill Dear Mr.Bahadori: This letter is CB&I's response to the Central Valley Regional Water Quality Control Board (CVRWCQB) staff email of November 25, 2014; requesting a work plan that reflects the design change for well MW-6 and describing the rational for the design change. In addition, this letter provides geologic evidence that a continuous water bearing zone exists beneath the Foothill Sanitary Landfill. Attached are two cross sections (A-A' and B-B')that show the continuous water bearing zone at the site. These cross sections were prepared using all of the groundwater wells at the site. Revised Work Plan The previous work plan for the installation of well MW-6 showed a single screened interval. This revised work plan is for the installation of MW-6 with a double screened interval as shown on the figure in Attachment A. The differences between in the design of MW-6 in this revised work plan and the previous work plan is as follows: • The diameter of the revised well design is 4-inches(in)as opposed to the previous 2-in diameter. The larger diameter allows for the installation of the water level sounding tube on the inside of the well as opposed to its previous installation in the bore hole. By placing the sounding tube inside of the well, makes for a better and more secure placement of the bentonite seal between the bore hole and the well casing. • The larger diameter also allows for the placement on an inflatable packer inside of the well to provide a hydraulic barrier between the two screened intervals. Photos of the packer are provided in Attachment B. Mw-6 Design.aocx