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• Corporation <br /> 005 Port Chicago Highway <br /> Concord, CA 94520-1120 <br /> Tel. 925.288.9898 <br /> Fax.925.288.0888 <br /> thew/g'1`"oup <br /> A dlember of The IT Croup <br /> su <br /> March 9, 2001 <br /> Margaret Lagorio, R.E.H.S. <br /> San Joaquin County Public Health Services <br /> Environmental Health Division i <br /> 304 E. Weber Avenue, Third Floor <br /> Stockton, California 95201 <br /> (209)468-3449 <br /> Fax: (209)464-0138 <br /> Re: Additional Information for Justification for Use of Pressure Grouting Domestic Well Decommissioning at 233 <br /> Parallel Avenue, Ripon, California <br /> Dear Ms. Lagorio: <br /> After you initially reviewed IT Corporation's December 5, 2000 Technical Justification for Use of Pressure Grouting, <br /> Domestic Well Decommissioning at 233 Parallel Avenue, Ripon, California, you requested additional information on <br /> the City of Ripon wells 4, 7, and 9. The Department of Water Resources (DW R)has not yet been able to provide <br /> the information for those wells because their files are being scanned. I have been able to collect some of the <br /> information from the City of Ripon and have included it with this letter. The City has a video log of well 4 (MW-4) <br /> that shows that the well is screened in the following intervals: 50-65, 90-105, 205-225, and 240-245 feet below <br /> ground surface (bgs). These correspond to the B-, A-, and D-aquifers. The City has been unable to locate a well <br /> completion report or well log for this well, installed in 1958. For City well 7 (MW-7)the test hole well log and electric <br /> well log are included with this letter. MW-7 is screened over the intervals 80-120, 142-163, and 188-196 feet bgs, <br /> which corresponds to the A-, C1-, and C2-aquifers. The same type of information is attached for City well 9 (MW- <br /> 9). MW-9 is screened from 170-200 feet bgs, which is considered the C2-aquifer. <br /> Due to the fact that MW-4, which has a production rate of 700 gallons per minute(gpm), is screened over both the <br /> B- and A-aquifer zones, interconnection is created between the B-and A-zones, although low permeable units <br /> separate the two zones at this particular location. Note also that MW-7 interconnects deeper zones. <br /> The borehole log for the M-5 cluster(attached) in Environmental Resource Management's (ERM) Exploratory <br /> Boring and Well Installation Report, Ripon, California, dated January 22, 2001 confirms IT's interpretation that the <br /> B-and A-zones are interconnected. The log shows sand from 50 to 120 feet bgs. Also, it is evident on the cross- <br /> sections provided to you in the December 5, 2000 letter that the B- and A-zones are interconnected below the <br /> former Nestle facility, which is also indicated on the borehole log for the new well cluster M-28 (also attached to this <br /> letter)to the west of the site, which shows sand from 0— 111 feet bgs. <br /> We believe that the additional information provided here, along with the substantial evidence in the December 5, <br /> 2000 letter, is sufficient to warrant granting a variance for decommissioning this well by pressure grouting without <br /> well casing perforation. <br /> Siincey,Hnd rff <br /> Project Hydrogeologist <br /> IT Corporation <br /> C: Binayak Acharya, Nestle USA, Inc. <br /> Marcus Pierce, California Regional Water Quality Control Board <br /> Attachments: Well data and a-logs for MW-7 and MW-9; borehole logs for M-5C1/M-5C2 and M-28-A/B/C1 <br />