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v v San Joaquin County Aou�N Environmental Health Department DIRECTOR Donna Heran, REHS 600 East Main Street c PROGRAM COORDINATORS Stockton, California 95202-3029 Margaret Lagorio,RENS .: :. Robert McClellon,REHS Website: www. ov.or /ehd Jeff Garruesco,REHS,RDI S 4:i F OR�i 1g g Kasey Foley,REHS Phone: (209)468-3420 Fax: (209)464-0138 October 8, 2009 Ms. Beverly Garcia Raymond Investment Corporation Post Office Box 567 Stockton, California 95201 Subject: Raymond Investment Corporation 730 Channel Street Stockton, California 95202 The San Joaquin County Environmental Health Department (EHD) has reviewed Additional Vapor and Groundwater Monitoring Well Work Plan, dated August 4, 2009, submitted by Condor Earth Technologies, Inc. (Condor) on your behalf. In the work plan, Condor proposes to install seven groundwater monitoring wells and three soil vapor wells at locations illustrated on Figure 3 of the work plan. Condor proposes to install monitoring well MW-4D, screened between approximately sixty-five and seventy-five feet below surface grade (bsg), adjacent to the southwest parameter of MW-4. Condor suggests that the analytical data for groundwater collected from proposed well MW-4D will support or discount the analytical data reported for grab groundwater samples collected in September 2006 from soil boring SB-7 at seventy-two feet bsg. The EHD approves the installation of MW-4D to define the vertical extent of contamination in groundwater and recommends that the well be screened between sixty and seventy feet bsg based on soil lithology for borehole SB-7, that demonstrates the presence of a sand unit at approximately sixty-one to sixty-two feet bsg; and includes sample interval of the SB-7 grab groundwater (sixty-eight to seventy-two feet bsg). Condor proposes to install MW-5 approximately twelve feet northeast of MW-4 with a twenty- five to forty degree angle toward the northeast and under the building facing North Grant Street. The well is proposed to be screened between approximately thirty and forty-five feet bsg. The EHD approves the installation of MW-5, down gradient of the source area, but recommends that MW-5 be installed with a vertical borehole, screened between approximately twenty-five to forty- five feet bsg, and located as near the east building as is practical. The EHD recognizes that wells installed at an angle can be problematic; also, as noted in the work plan and quarterly reports, groundwater has historically varied between thirty-one and thirty-seven feet bsg. Noting that the most contaminated well, MW-4, is screened between twenty-five and forty-five feet bsg, and groundwater is currently at approximately thirty-one feet bsg, the EHD believes it best to install MW-5 and the other proposed shallow wells at the same screened interval as MW-4.