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San Joaquin County �a.!!+N a1RFcraR -. Environmental Health Department Donna Reran,RENS 600 East Main Street PROGRAM COORDINATORS Stockton, California 95202-3029 Robert McClellon,REHS �=: s Jeff Carruesco,REHS,RDI • Kasey Foley,REHS P Website: www.Sjgov.org/ehd Linda Turkatte,REHS F0�� Phone: (209)468-3420 Fax: (209),464-0138 November 10, 2011 Mr. Sergio Morescalchi Ms. Shelby Lathop Atlantic Richfield Company ConocoPhillips Company Post Office Box 1257 76 Broadway San Ramon, California 94583 Sacramento, California 95818 Subject: 76 Service Station No. 11193 LOP Case No: 1129 3202 West Hammer Lane Stockton, California Dear Mr. Morescalchi and Ms. Lathop: The San Joaquin County Environmental Health Department (EHD) has received and reviewed Well Destruction Work Plan, dated 31 October 2011, submitted by your consulting firm, Stantec Consulting Corporation (Stantec), on your behalf. The EHD had directed the submittal of a work plan to destroy the 23 wells associated with your site by letter dated 19 October 2011. In the work plan, Stantec proposes to check each well for obstructions, and if found, remove the obstructions prior to destroying the well. Stantec proposes to over-drill and remove the materials used to construct impacted monitoring wells MW-3 through MW-5, MW-8, MW-9, MW-13 and vapor well VW-1; and pressure-grout monitoring wells MW-1 R, MW-2R, MW-6, MW-7, MW-10 and MW-11. Stantec cites health and safety concerns for their proposal to destroy MW-7 by pressure-grouting since MW-7 is located in the sidewalk on the north side of West Hammer Lane, near a busy intersection. Of the wells proposed by Stantec to be pressure-grouted and based on soil and groundwater analytical data, the EHD only approves the pressure-grouting of MW-6, MW-10 and MW-11 in the manner presented by Stantec in the work plan. Although the work plan does not mention the amount or duration of pressure applied to the grout, the EHD recommends that 25 pounds per square inch (PSI) of liquid-grout pressure be applied for ten minutes. Monitoring wells MW-IR, MW-2R and MW-7 must be destroyed by drilling out the well contents since these wells are known to be impacted based on current groundwater data, and/or their location with respect to known or suspected residual contamination. Stantec proposes to destroy the ten sparge wells, OS-1 through OS-10, by pressure grouting. Since these ozone sparge wells are in an area of known petroleum hydrocarbon contamination, the EHD will not approve that these wells be pressure grouted, with the exception of OS-5. The EHD approves the pressure-grouting of OS-5 in the manner proposed by Stantec in the work plan since OS-5 is near a power pole and beneath low hanging wires where access is limited. The remaining ozone sparge wells must be destroyed by drilling out