SITE INFORMATION AND CORRESPONDENCE FILE 2

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San Joaquin County DIRECTOR Donna Heran, REHS Environmental Health Department ASSISTANT DIRECTOR ~ � e 600 East Main Street Laurie Cotulla,REHS y Irrilll` { Stockton, California 95202-3029 PROGRAM COORDINATORS Mike Huggins, RENS,RDI P Margaret Lagorio,REHS Cq �� Website: www.sjgov.org/ehd Robert McClellon,REHS �fFOR Phone: (209)46$-3420 Jeff Can-uesco,REHS,RD] Fax: (209)464-0138 Kasey Foley,REHS February 6,2009 Mr. Sergio Morescalchi Atlantic Richfield Company Post Office Box 1257 San Ramon, California 94583 Subject: ARCO Service Station No. 2186 3212 North California Street Stockton, California 94570 The San Joaquin County Environmental Health Department (EHD) has reviewed Addendum to IYork Plan for Vapor Probe Destruction, Well Destruction, and Well Installation (Addendum), dated January 26, 2009, prepared by Stantec Consulting Corporation (Stantec) on your behalf for the above-referenced site. The Addendum includes revisions for destroying soil vapor probes VP-1, VP-2, and VP-3, and installing two monitoring wells (MW-1R and MW-3R) screened across the first groundwater bearing zone, and one monitoring well (MW-1D) screened across a deep groundwater bearing zone. By letter dated December 3, 2008, the E11D approved the proposed method for destroying MW-1 and MW-3 and directed the submittal of an addendum to Nark Plan for Vapor Probe Destruction, Well Destruction, and Well .Installation (Work Plan) dated October 14, 2008. The EHD approves the destruction of soil vapor probes VP-1, VP-2, and VP-3 as proposed by Stantec in the Addendum. The three soil vapor probes will be over-drilled to total depth of approximately six feet below surface grade (bsg) and the borings will be grouted with neat cement from total depth to ground surface using a tremie pipe. The EHD also approves the installation of MW-IR and MW-3R as proposed by Stantec in the Addendum. The two shallow wells will be advanced to approximately fifty-eight feet bsg using eight-inch-diameter hollow-stem augers and constructed with a screen between approximately thirty-eight and fifty-eight feet bsg. Soil will be continuously cored from approximately thirty feet bsg to total depth for lithological evaluation and soil cores will be screened in the field for the presence of volatile organic compounds using a photo-ionization detector, Selected soil samples will be analyzed by an environmental laboratory certified by the State of California. Although Figure 2 of the Addendum illustrates that the shallow wells will be constructed using four-inch diameter schedule 40 poly vinyl chloride (PVC) casing, the EHD recommends that the wells be constructed using two-inch diameter schedule 40 PVC casing, as proposed by Stantec in both the narrative of the Work Plan dated October 14, 2008, and the narrative of the Addendum dated January 26, 2009. The EHD also recommends that #3 sand be used with 0.020-inch-slotted casing instead of the proposed 2112 sand.