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City of Stockton A68101.02A . July 21, 1995 Page 2 excavation bottom. Field screening with the PID of samples collected at 4 feet BSG on the - south end wall and at 5 feet BSG on the northwest wall indicated concentrations of VOCs of 2 and 3 ppm respectively. Twining expressed a concern about the volume of water in the excavation and how to dispose of it. Therefore the client made a decision to temporarily stop excavation work and formulate a plan to deal with the water in the excavation. A sample of the water in the excavation was collected for chemical analysis in the laboratory. The water sample was analyzed for gasoline constituents and the results of the analysis are summarized in Table 1. Table 1 -` Groundwater Sample Analytical Results Dated Sampling. '64/bS/95 ::. sample larauon ..: ' :rug71- .... ...',..{fi/t- :.;►��. ..;<'. �� ..: Excavation 1,000 2,000 800 6,400 17,000 DLR 50 So so So 5,000 BTBX = benzene,toluene,ethylbenzene,and xylenes TPH-G = total petroleum hydrocarbons-gasoline range constituent pg/L = microgram per liter DLR = Detection limits For reporting purposes. Note: Detection limits for these analyses are provided in the attached laboratory reports. The west end of the excavation was partially backfilled with pea gravel on April 5 by the excavation contractor, TBI Engineering, Inc. This backfill was placed at the direction of Mr. John Fukumoto of The City of Stockton. Soil removed from the excavation was stockpiled at the location shown on Drawing 1. Based on the concentrations of gasoline constituents detected in the groundwater sample collected from the excavation, it appears that PPCs have impacted groundwater. Furthermore, the groundwater elevation precluded assessment of the extent of PPCs migration in soil around the former UST's and dispensers locations. Therefore, it appears prudent to conduct additional work to complete the soil assessment and attempt to remove the soil impacted with PPCs. I -7