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�� KLEINFELDER November 5, 1990 File: 24-220025-000 Mr. Steve Rosenbaum Regional Water Quality Control Board 3443 Routier Road Sacramento, CA 95827-3098 SUBJECT: ABANDONMENT OF MW -4 AND MW -9 FORWARD SANITARY LANDFILL STOCKTON, CALIFORNIA Dear Mr. Rosenbaum: Due to the westward expansion of landfill facilities at Forward Landfill, we wish to abandon two monitoring wells, MW -4 and MW -9. At this time, only MW -4 is being monitored under the provisions of Monitoring and Reporting Program 89-148. MW -9 was dropped from the program in 1989 after four sampling rounds were completed. MW -4 is relatively shallow (70 feet deep) and has been dry since May 1990. Well construction details for MW -4 and MW -9 are shown on Table 1, which is attached. The area surrounding MW -4 and MW -9 has been excavated to an approximate depth of 25 feet. MW -4 and MW -9 are intact, apparently undamaged, and are in the middle of an "island" of undisturbed ground. We propose to abandon the two wells as follows: o A 3 percent bentonite/cement grout will be pumped up to each well head and into the well through a tremae hose. The volume of grout required to fill each well casing will be computed prior to grouting and the actual volume used will be monitored to assess whether the entire well casing has been filled. o The grout will be allowed to cure for a minimum of 72 hours. o The 25 -foot column of soil surrounding MW -4 and MW -9 and the top 25 feet of each well will be removed. o The ground around MW -4 and MW -9 will be excavated an additional five feet below the new ground surface, and the two casings will be removed to the bottom of the excavation. The excavation will then be backfilled with native soil. These procedures are in accordance with Bulletin 74-90 of the California Department of Water Resources (January 1990). KLEINFELDER 9795 Business Park Drive, Sacramento, CA 95827 (916) 366-1701