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I is approximately 10 feet above the historically highest recorded groundwater level in the site area (35 feet in 1983) 3.0 DRILLING AND SAMPLING PROCEDURES 3.1 Drdlmg I On September 9, 1995, V & W Drilling of Rio Vista drilled and installed moiutonng well VM-1 (Figure,2) A rotary concrete cutter was used to cut a 16-inch diameter hole through the concrete so that a well box could be installed The well was drilled with a Mobile Drill B-61 ng with 8-inch-diameter hollow-stem augers Drill cuttings were added to the existing soil stockpile that was generated during previous excavation and I drilling (Figure 2) The well was drilled to a depth of 70 feet, but was subsequently backfilled with a bentonite-cement mixture to a depth of 67 feet, approximately 15 feet below the static water level The augers were then steam-cleaned, and the auger rinseate water was contained in two 55-gallon drums Inear the soil stockpile 3.2 Soil Sampling Soil samples were collected every 5 feet, using a spht-spoon sample barrel loaded with clean brass sample tubes A geologist from Upgradient examined the samples, screened them for organic vapors using a Microtip BL2000 photo-ionization detector, and prepared a boring log (see Appendix A) The number of percussion hammer blows needed to drive the sampler 18 inches into the native soil was recorded on the boring log, along with the PID reading and a description of the sample The bottom tube from each sample was'capped, sealed, labelled, and placed in a cooled ice chest prior to shipment to Inchcape Testing Services in San Jose,'California The chain-of-custody form is included in Appendix B 3.3 Well Completion The well was completed as a 2-mch-diameter groundwater monitoring well (Appendix A) Pnor to installing the screened casing, the depth to groundwater was measured several tines to insure that the water level had stabilized Initially, saturated conditions were first encountered in a clay bed at a depth of 60 feet After approximately 20 minutes, groundwater stabilized at 50 feet To insure that at least 3 feet of screen extends above the static water level, 20 feet of screened casing were installed between the depths of 47 and 67 feet The sand pack extends from 67 to 45 feet, and hydrated bentonite extends from The previous owner was *** 45 to 43 feet The well was grouted from 43 feet to the surface with Portland cement, and a well box was installed flush with the concrete , I , r 4 2 r