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k 1 September 11, 2000 50441 Mr. Vidal Pedraza San Joaquin County Public Health Service Environmental Health Division (PHS/EHD) Page 3 Harding Lawson Associates On April 26 and 28, 2000, HLA contacted Mr. Doug Wilson of the San Joaquin County Public Health Service Environmental Health Division (PHS/EHD), UST Group regarding the appropriate course of action. HLA summarized the above information and specifically discussed HLA's proposed approach to remove the sand in the USTs prior to lifting the USTs out of the excavation. Mr. Wilson indicated that a pre -removal assessment would be required for PHS/EHD to view site conditions prior to removal of sand from the USTs and prior to the subsequent equipment mobilization for normal UST -removal sampling as directed by PHS/EHD. Prior to commencement of work, HLA submitted to the PHS/EHD a permit application dated June 2, 2000 (HLA, 2000a). The permit application included a work plan (HLA, 2000b), that described procedures to be used and a site-specific Health and Safety Plan (HLA, 2000c) that was prepared consistent with the requirements of Title 8 CCR 5192. PHS/EHD approved the permit application, and issued the UST Removal Permit on June 14, 2000. As required by PHS/EHD, HLA also submitted a work plan for over -excavation and sampling (HLA, 2000d) to Ms. Margaret Lagorio of the PHS/EHD, Site Mitigation Group as a contingency plan in case over -excavation of impacted soil was required. On June 21, 2000, a pre -removal site meeting to assess site conditions was attended by Mr. Vidal Pedraza of the PHS/EHD, Mr. Kent Miller of the SFPD, Mr. Ray Henry of RAH Environmental (UST removal ' contractor), and Dr. Gary D. Haeck of HLA. After observing HLA collect readings of the oxygen content and lower explosive limits (LEL) of the atmosphere within the USTs, Mr. Pedraza (PHS/EHD) and Mr. Miller (SFPD) approved the approach of removing the sand within the USTs prior to lifting the USTs out of the excavation. ' Removal and backfill/compaction activities were performed intermittently between June 26 and July 17, 2000, by RAH Environmental Incorporated, (RAH) (License number 592216 A-HAZ) of Loomis, California, ' under the direction of HLA. All work was performed in accordance with the UST Removal Permit, the Work Plan (HLA, 2000b), and the Health and Safety Plan (HLA, 2000c). Prior to commencement of removal activities, the Site was cleared for the presence of subsurface utilities by Underground Service Alert. PRE -REMOVAL ASSEMENT OF SITE CONDITIONS ' As discussed above, a pre -removal site meeting was held on June 21, 2000 and attended by representatives of the PHS/EHD, SFPD, RAH, and HLA. Because HLA's proposed approach included removing the sand within the severely -rusted USTs prior to lifting the USTs from the excavation, PHS/EHD required a pre- removal assessment of site conditions. At the request of PHS/EHD, HLA collected measurements of oxygen content and lower explosive limit (LEL) from the atmosphere within the USTs with a GasTech Model 1314 GasTechTor which had been calibrated to a hexane standard. This information is summarized in the following table. 4