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Soil and Groundwater Investigation Report and Second Quarter 2005 Monitoring and Sampling, US Can-Welty Road October 2005 and absentee property owner. Based on the evidence and uncertainties of possible USTs, Chevron and the RWQCB agreed that an additional boring/well was not necessary at this location during this phase of the investigation. An SAIC field geologist observed Precision Sampling, Inc. (Precision), of Richmond, California(C57 #636387)advance the soil borings to a depth of 50 feet bgs using a direct-push drill rig and to install groundwater monitoring well MW-5 using hollow stem augers. Prior to advancing the soil borings and the well,each boring was hand cleared to a minimum depth of 8 feet bgs. The soil borings were ` continuously cored from 8 feet bgs to the total depth. Borings were explored using 4-foot sections of 2 inch-diameter tube with a poly-acrylic liner. The probes were advanced directly into the soil and, on retrieval, the poly-acrylic liner was removed; the soil core was inspected and, under the supervision of a California Professional Geologist or Professional Civil Engineer, logged according to the Unified Soil Classification System (USCS) in accordance with American Society for Testing and Materials D 2488 standards. The soil core was field screened for the presence of organic vapors using a photoionization detector(PID)and recorded on the boring logs. Well boring MW-5 was advanced within five feet of SB- 15 and soil cores were not collected. However,as well boring MW-5 was advanced, SAIC field geologists collected control samples for lithologic comparison between the well boring and SB-15. Well MW-5 was drilled to the depth of 45 feet bgs. Soil encountered in the borings consisted of mixtures of clay, silt, and sand. Depth to first-encountered groundwater during the 2005 investigation was observed between 31.25 and 38.5 feet bgs. A perched water zone, 1 to 2 feet thick,was observed in SB-15 at 12.5 feet bgs. Soil boring logs containing PID readings, USCS descriptions, well construction details,and other pertinent drilling data are included in Appendix E. All down-hole equipment was decontaminated between borings using a Liquinox solution and steam cleaned using potable water. On completion,all soil borings were abandoned by backfilling with cement grout to ground surface in accordance with SJCEHD procedures. SJCEHD was contacted prior to abandonment,and permission to proceed with boring abandonment was granted. Soil boring locations are presented on Figure 2. 4.3.1 Soil Sample Collection Generally, soil borings were advanced to a target depth of 50 feet bgs. The deepest soil sample was collected at 47 feet bgs from soil boring SB-I5 to delineate the vertical extent of petroleum-affected soil. Typically, soil samples were collected from each boring from the most petroleum-affected soil interval based on visual observations and PID readings, or from the depths that corresponded with the depths of petroleum-affected soil from neighboring borings. Soil samples were retrieved from the Dual Tube liner by trimming the desired interval and sealing each end with Teflon sheets and plastic end caps. The samples were immediately labeled and placed in an ice-cooled chest pending analysis. To support a future Human Health Screening Evaluation (HHSE), SAIC also collected shallow soil samples from select borings at depths between I foot and 5 feet bgs. All shallow soil samples were ` collected using an AMS core sampler lined with a 2 inch-diameter brass tube. The lined core sampler was driven into the subsurface using a 10-pound slide hammer. On retrieval, the brass tube containing the soil sample was removed from the core sampler and each end was sealed with Teflon sheets and plastic end caps. The samples were immediately labeled and placed in an ice-cooled chest pending analysis. The ` hand auger and core sampler were decontaminated between sampling locations. Twelve soil samples were submitted for laboratory analyses from depths ranging from 1 foot to 47 feet bgs. ` 4.3.2 Grab Groundwater Sampling SAIC collected three grab groundwater samples from boring locations SB-13, SB-14, and SB-17 for analyses of petroleum constituents. Grab groundwater samples were collected by inserting new polyvinyl v L 5 From Science to Solutions,- 6.