ARCHIVED REPORTS_XR0011922 - Laserfiche WebLink

Home Browse Search

F iPage 2, G11hes 10/17/94 concentrations of gasoline, diesel, and aromatics were also detected in the water sample from MW-1 A domestic water well (G-1) located near the shop building was also sampled, but no hydrocarbons were detected ' 3.0 MONITOR WELL INSTALLATION I3.1 Drilling and Sampling Procedures On September 1, 1994, the drilling and installation of two monitor wells was undertaken A Mobil Drill B-53 rig equipped with 8-inch hollow-stem augers was provided by V& W Drilling of Rio I Vista, California Soil samples were collected at 5-foot intervals using a California modified split-spoon sampler loaded with three brass sample sleeves The bottom sleeve was preserved for ' laboratory analysis by covering the ends with teflon sheets and plastic caps and sealing with duct tape Soil was extruded from the middle and upper sleeves into a plastic bag and screened for the presence of volatile organic hydrocarbons, using a Photovac Microtip HL-2000 photo-ionization detector PID readings and soil descriptions were then recorded on the boring logs (Appendix A) �-- 6 1 Selected samples were transmitted under chain-of-custody to McCampbell Analytical for analysis Eight(8) soil samples were analyzed for TPH-gasoline, TPH-diesel, and BTE&X A summary of the results is presented in Table 1 The actual laboratory data are provided in Appendix B I Both borings were completed with 2-inch diameter PVC casing The lowest 25 feet of casing ' were completed with 010 perforated screen The details of the well construction are shown in Appendix A ' 3,2 Subsurface Geology Soils encountered during drilling were mostly dark brown silty,clay to clayey silt Both borings Iencountered intermittent porous layers or lenses of very-fine to coarse well-sorted sand, with an occasional poorly-sorted coarse sand or gravelly zone The porous.layers were encountered at irregular depths and did not exhibit characteristics that would allow layers in one well bore to be correlated with similar layers from another well bore lased on drill rates and the number of impacts required to drive a California modified split-spoon sampler, subsurface soil consolidation was generally firm to stiff from the surface to about 55 feet From 55 to about 65 feet, drilling was difficult and the litholgy consisted of well-cemented clayey silt Below 65 feet, the soil resembled the soil above 55 feet, but was slightly more consolidated I ' Two definable sequences can be identified in the boring logs The upper sequence, from the surface to a depth of approximately 60 feet, consists primarily of silty clay, except for a fine-grained sand bed between 35 and 45 feet In general, this sequence has moderate permeability and is recognizable in all four borings drilled to date On the San Jose Sheet ofthe