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IT Corporation 4011:; Ron Chi,ar, Ili-rim.' Illi MVV/� lJ � TrL 0_'5. '88.0814S i I Fas. 92.i._288.0888 the ; OUP IAN 0 3 2001 A1/rndmr rl TiuIT Cnnq, EL,j riONMENT HEALTH PERMIT/SERVICES December 5, 2000 Marcus Pierce, R.G., C.Hg. California Regional Water Quality Control Board-Central Valley Region 3443 Routier Road, Suite A Sacramento, California 95827-3098 Re: Technical Justification for Use of Pressure Grouting Domestic Well Decommissioning at 233 Parallel Avenue, Ripon, California Dear Mr. Pierce: On behalf of Nestle USA, Inc., IT Corporation is providing a technical justification for using pressure grouting to decommission the domestic well located at 233 Parallel Avenue in Ripon, California. By way of background, the hydrostratigraphy surrounding 233 Parallel Avenue is summarized as consisting of three major water-bearing zones: the Uppei Sand Zone, the Clay Zone, and the Lower Sand Zone. The attached Table 1 shows this generalized hydrostratigraphy. The Upper Sand Zone generally consists of, in increasing depth: the uppermost saturated sand unit (the B-aquifer) at a depth of approximately 25 to 70 feet below ground surface (bgs), a discontinuous silty clay aquitard, and a thick sand and gravel unit (the A-aquifer) at a depth of approximately 85 to 120 feet bgs. The Upper Sand Zone is underlain by the Clay Zone, which is comprised of alternating sand, silt, and clay units, and contains two laterally continuous sand units: the upper sand unit (CI-aquifer) and the lower sand unit (C2-aquifer). The Clay Zone is found approximately between the depths of 120 to 220 feet bgs. The lowest clay unit of the Clay Zone is known as the "blue clay", named after its distinct bluish-green color. Beneath the blue clay is the Lower Sand Zone (D-aquifer) which is typically coarser-grained than the sands found in the Clay Zone. The sands and gravels in the B- and A-aquifers occur throughout the area surrounding 233 Parallel Avenue. The silt and clay aquitard between the B- and A-aquifers (B/A aquitard) appears to thin to the east-northeast of the former Nestle facility (M-1 and M-5 boring logs). The Clay Zone also appears to be continuous throughout the area, with the CI-aquifer occurring regionally between 10 to 25 feet below the top of the Clay Zone. The C2-aquifer occurs at a deeper interval within the Clay Zone. The attached Cross Section A-A' demonstrates these hydrostratigraphic characteristics. Cross section A-A' runs through the Nestle property and also through the closest logged location to the 233 Parallel Avenue domestic well (the M-5 well cluster). On September 26, 2000, IT requested that you approve our recommended method of using shot strings to perforate the 233 Parallel Avenue well casing three feet above and three feet below the