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(100 mg/kg for TPH) was attained at the excavation sidewalls and bottom or until building structures prevented further excavation ' Prior to backfilling, the saturated bottom of the excavation was stabilized by placing a 4-foot-thick rock base, consisting of 1- to 2-inch-diameter rock, over a geotextile fabric liner The excavation was then backfilled ' with clean fill dirt and compacted using construction equipment The backfill area was subsequently paved with asphalt cover 1 Additional Characterization As discussed above, in September 1994, Catellus conducted additional soil sampling within the former excavation footprint and underneath the 1 existing building to verify that residual hydrocarbon concentrations, if present in site soils, would not pose a significant risk to human health and the environment The results of the additional characterization activities ' were presented in the Environmental Conditions Report (ERM, July 1995) The data collected during this investigation verified the accuracy of the 1993 excavation confirmation sampling and supported the 1993 confirmation sampling results that indicated that soils exceeding the TPH cleanup goal had been excavated Figure 3-2, which is reproduced from the July 1995 report, illustrates the TPH concentrations detected in soils in the former Tank Site #2 area The data indicated that a limited volume of soils containing TPH at levels higher than the 100 mg/kg cleanup goal were present beneath the building at Former Tank Site #2 within the interval of approximately 5 to ' 11 feet bgs The estimated extent of these elevated TPH detections is f-- illustrated in Figure 3-3 The total estimated volume of TPH-impacted soil beneath the former warehouse footprint is approximately 210 cubic yards Ground Water Monitoring and Extraction Events ' The originally selected ground water remedial alternative for Former Tank Site #2 involved extraction of a fixed volume of hydrocarbon- containing ground water from existing monitoring wells Ground water was extracted from monitoring well MW-1A during three events December 1993/January 1994, May 1994, and September 1994 The ' ground water extracted during each event was pumped into Baker tanks for temporary storage and subsequently transported via vacuum trucks to the City of Stockton Publicly-Owned Treatment Works (POTW) for direct ' discharge In October 1996, oxygen regenerating compounds (ORC) were • 3-7