SITE INFORMATION AND CORRESPONDENCE FILE 2

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ARCO #2130 Page 2 of 3 7906 N. EI Dorado Street September 18, 2014 i Stockton, CA 95210 The EHD approves the work plan with the following conditions: • Use only potable water to mix the grout; groundwater displaced from the wells or borings may not be used in grout or for any other purpose and must be properly disposed; • When over-drilling , it is not necessary to widen the diameter of the top 3 feet of the borehole by one foot than the original auger used to install the well , nor is it necessary to install a mushroom cap. However, wells must be drilled to total depth during the drill-out process; • MW-15 boring log shows a boring depth of 50.5 feet bgs and MW- 16 boring log shows a boring depth of 51 . 5 feet bgs. However, Table 1 of the Well Destruction Work Plan shows a boring depth of 50 feet bgs for both wells; both wells must be drilled to their total depths; • Use a tremie pipe when backfilling over-drilled boreholes from the bottom up as described in the work plan ; • Apply at least 25 psi of pressure on the grout for ten minutes when pressure grouting the wells ; destroy the wells by over-drilling if the well casings are unable to withstand this pressure for this length of time; • Following pressure grouting , enlarge the diameter of the top three feet of the borehole at least one foot larger than the auger originally utilized to install the well; cut off and remove the casing six inches above the bottom of the excavation before inserting the grout as described in the work plan ; • In addition to the two bullet points above, and except the borehole diameter enlargement requirement, Stantec may install a limited mushroom cap within the borehole diameter of the following 15 wells: MW-5, MW-6, MW-13 , MW-16, MW-20, AS-2, AS-3, VW-3, VW-6, VW-8 through VW-12 , and MS-3A/B . • The 12-inch polyvinylchloride (PVC) conductor casing in wells AS-2 and AS-3 may be left in place during destruction activity; • Notify the EHD at least two weeks prior to implementing fieldwork so that an inspector can schedule to be present for the well destructions ; and • Include the signed and dated manifests for soil and groundwater waste removal and disposal when submitting the final well destruction report. During the public participation period, which ended on 01 December 2013, EHD received no comments or concerns from interested individuals and agencies regarding the pending closure of this site. You may proceed with the well destructions if in compliance with the conditions noted above . i