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I <br />` 4. Chronology of Events: One UST (1 diesel 10,000 gallon) removed on November 13, 1998. <br /> UST was disposed of at Erickson Inc., Richmond, California. All piping was removed. <br /> Petroleum hydrocarbon contaminated soil was overexcavated (-20 cubic yards). Two soil <br /> samples were collected from beneath the UST (Figure 6) and from the soil stockpiles for <br /> analysis. The stockpile was subsequently used to backfill the excavation. <br /> The site investigation began on August 24, 1999. One soil boring (Bl)was advanced to 40 . <br /> feet below ground surface (bgs) and three soil borings (132, 4, 5) were advanced to 30 feet <br /> bgs. Groundwater was not encountered. The highest depth to groundwater at this site was <br /> about 38 feet bgs. Water identified to be from a former locomotive washing facility that was <br /> adjacent to the former locomotive fueling facility was found at less than two feet bgs in one <br /> attempted boring(133). A sample ofthe water was collected from B1 for analysis. The soil <br /> samples had no odor except for the samples from 15 and 20 feet bgs in boring B1. <br /> f On October 13, 1999 PHSEHD requested submittal of calculation of mass remaining at the <br /> site, and fate&tran`sport modeling PHSEHD received the Fate& Transport Model Report. <br /> k Upgradient concluded in the report that the contaminant impact was not a threat because it is <br /> of limited extent,the contaminant is low-solubility and its vertical movement is impeded by <br /> the fine-grained subsurface. <br /> In September 2007 PHSEHD notified .ST&E that additional site assessment work was <br /> E required. ST&E retained this office in November, 2007 to submit a workplan and conduct <br /> i <br /> required site assessment work. <br /> i <br /> i <br /> 5. Site Stratigraphy and Hydrogeology: Stratigraphy of upper 70 feet bgs at site consists of dark <br /> brown clayey silt and interbedded fine grained sand. Local clay beds are present(Figure 11) <br /> and Appendix 4). The first water bearing zone is contained within the fine to medium <br /> grained sand at a depth of about 60 feet bgs. <br /> EnvironmentallSTE1PARSCR09102008.wpd 1$ <br /> i <br /> i <br /> i ,. <br />