SITE INFORMATION AND CORRESPONDENCE

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Chronology Federal Building 401 North San Joaquin Street Stockton CA 95202 Site Code: 505260 The site is located at the intersection of Lindsey Street and San Joaquin Street on APN 139-150-05. The site consists of a parking area,a landscaped area,and a building which houses a postal facility and federal offices. The investigation was initiated as a pre-tank removal assessment in June 1994. The underground tanks were reportedly installed in 1932 and filled with sand in 1960. The tanks were removed in 1995 and a limited excavation was attempted. The remaining soil contamination was investigated in 1996 which included.the installation of a groundwater monitoring well. Groundwater samples were collected which did not indicate groundwater contamination. William W.Millar,Registered Geologist#6178 recommended,based on the occurrence of a 3 -5 foot thick clay layer located at 30-35 feet below ground surface;that the site be certified as requiring no further action and the monitoring well be destroyed. William W.Millar's recommendations were reported in the"Soil and Groundwater Investigation"dated November 1996 and the"Addenda to Soil and Groundwater Investigation Report" dated April 11, 1997. PHS/EHD concurs with the recommendation to certify the site as requiring no further action, once the on site monitoring well is destroyed under PHS/EHD permit. 1994 6/30/94 Four soil borings,131,B2,B3,and B4 were drilled and sampled. The results were reported in the "Subsurface Investigation Report"dated August 19, 1994. Soil contamination was evidenced,but appeared to attenuate to non-detect at 25 feet below ground surface(bgs). The analytical results (corrected date)and boring logs are attached. 1995 5/4/95 The first underground storage tank was removed this date,#39-501588-02. Tank#2 was a 5,000 gallon riveted tank which upon removal was noted to be in very.bad condition. The center seam was split top to bottom. 5/8/95 Excavation was initiated in the area of Tank#2. Soil samples were collected on May 10, 1995. Remaining soil contamination was evidenced. The analytical results were reported in the"Analytical Summary Tank Excavation"dated July 14, 1995 and are attached with a map of the excavation. 6/14/95 The second underground storage tank was removed this date,#39-501587-01. Tank#1 was a 5,000 gallon riveted tank which was partially filled with sand. Additional excavation occurred following the removal of the second tank and soil samples were collected on June.164 1995. The excavation was subsequently backfilled with pea gravel to approximately four feet bgs.The analytical results were reported in the"Analytical Summary Tank Excavation"dated July 14, 1995 and are attached with a map of the excavation. 1996 7/8/96 Five soil borings were drilled and sampled,one of which was converted into a monitoring well, MWI and the four soil borings were identified as B1 -B4. The analytical results were reported in the"Soil and Groundwater Investigation"dated November 1996. Two groundwater sampling events occurred in 1996. The boring logs(corrected date)and analytical'results(revised January 1997)are attached. 1997 3/21/97 Groundwater samples were collected from MW1 on this date and the analytical results were reported in the"Addenda to Soil and Groundwater Investigation Report"dated April 11, 1997. The groundwater sample results from all three sampling events are attached. w r V