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4.0 FIELD INVESTIGATION 4_1 Soil Borings On November 26 and 27, 1996, a total of eight soil bonngs (SB 1 through S138) were advanced to depths ranging from approximately 20 5 to 45 5 feet bgs under the supervision of Smith Technology The boring locations are shown on Figure 2 Vironex Environmental Field Services of Hayward, California (C57# 705927) advanced the bonngs using Direct Push Technology (DPT), specifically the Geoprobe Systems Model 5400 sampling system A field geologist was present to log all drill cuttings and soil samples utilizing the Unified Soil Classification System Descriptions of soil types encountered and sample collection intervals were recorded on boring logs included in Appendix I Soil samples were collected every 5 feet in brass tubes Soil samples were field screened with a flame ionization detector(FID) Sample tubes were immediately sealed ' at each end using Teflon tape and plastic end caps, labeled, and placed on ice Subsequent to sample collection, the soil borings were grouted to the surface with a neat cement grout Drill cuttings were placed on the on-site soil pile ' In general, two to three soil samples were collected from each boring for submittal to Argon Laboratories in Ceres, California (Certification No 1873) using chain-of-custody documentation The samples were analyzed for TPHg and benzene, toluene, ethylbenzene, xylenes (BTEX) by EPA methods 8015 (modified) and 8020, respectively In addition, one vadose zone soil sample from boring SB4 and two saturated zone soil sample from bonngs SB4 and S137 were submitted to PTS Laboratories, Inc of Santa Fe Springs, California for analysis of geophysical parameters using chain-of-custody documentation Copies of chain-of-custody records and laboratory data sheets are contained in Appendix II During advancement of the bonngs, groundwater samples were collected from the water table in borings SB5 and S137 using a stainless steel bailer in order to further define the lateral extent of ' groundwater contamination on site and off site In order to determine vertical extent of potential groundwater contamination in the vicinity of the Thornton Municipal Supply Well No 2, a hydropunch was used in boring SB7 to collect a groundwater sample at 28 feet bgs using a stainless steel bailer On November 26, 1997, Ms Mary Meays of PHS/EHD had requested while on-site that groundwater samples be collected from bonngs S135 and S137 The groundwater samples were submitted to Argon Laboratories using chain-of-custody documentation for analysis of TPHg and BTEX by EPA methods 8015 (modified) and 8020 Copies of chain-of-custody records and laboratory reports are contained in Appendix 11 5.0 RESULTS OF INVESTIGATION ' 5.1 Site GeoloY Site boring logs and sediments encountered while drilling indicate that the shallow soil beneath the site is consistent with soil encountered in previous bonngs on site The upper 5 to 10 feet of the soil column generally consists of silt Below 10 feet, fine to medium grained sand with w 194326Veportslsumrptdoc 3 SNR'H i