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` measured through October 26, 1998, is presented in Table l Copies of field observations documenting work performed at the site is presented in Attachment I Groundwater Analytical Results The distribution of groundwater sample analytical results obtained from monitor wells at the site on October 26, 1998, is presented on Figure 2 and summarized in Table 2 TPHg and BTEX were present at detectable concentrations in eight of the ten samples submitted for analysis Chemical analytical results indicate the highest concentrations of TPHg and benzene are in the vicinity of monitor well MW-1 TPH9 concentrations in groundwater samples ranged from 18,500 micrograms per liter (ug/L) in monitor well MW-1, to less than detectable levels in samples collected from monitor wells MW-7, N W-8, and MW-10 Benzene concentrations ranged from below the laboratory method detection limit (<0 5 ug/L) in monitor wells N W-7 and MW-10, to 430 ug/L in MW-5 MTBE was reported in one monitor well this sampling event with a concentration of 41 2 ug/L in a sample collected from monitor well MW-4 Attachment 11 contains photocopies of the laboratory analytical reports and the chain-of-custody form Purge Water Purge water generated during groundwater purging is currently contained on-site in Department of Transportation rated 55-gallon drums and will be removed to a disposal/recycling facility during January 1999 FORTHCOMING ACTIVITIES During the first quarter of 1999, SECOR will conduct additional well monitoring, purging, and sampling activities The results of these activities will be summarized in a quarterly monitoring report to be submitted to you in April 1999 This report presents our understanding of existing conditions at the subject site The conclusions contained herein are based on the analytical results and professional judgment which are in accordance with current standards of professional practice, no other warranty is expressed or implied SECOR assumes no liability for exploratory borings or data reported by other consultants or contractors Sincerely, '� B is .SECOR International Incorporated WCC ��. 0 No 60£3 Todd J Brown Jo n E Bower, R G �TFOF CAV�� Project Geologist Principal Geologist TJB/JEB tb Attachments cc Harlin Knoll, San Joaquin County Public Health Services Elizabeth Thayer, California Regional Water Quality Control Board SECOR D Mnie 01RL0CKF0 RD qm 498 2 ...vary.7 19" 7C00,001 011L0004