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' Bank of Stockton- Cutter Lumber Site Page 4 Groundwater Monitoring Well Construction I Project No 102 2 April 24, 1998 ' 2.0 FIELD SAMPLING AND DATA COLLECTION ' 2.1 Field Work - Monitoring Wells Drilling & Construction ' 2.1.1 Monitoring Well Drilling From March 2 through March 5, 1998 a BK-81 hollow stem auger drilling rig, owned and operated by V&W Drilling Co (C-57 #710678), was used to drill a total of 6 soil borings These were completed to a depth sufficient to penetrate into the saturated zone, which historically has occurred at a depth of about 30 to ' 40 feet below grade The borings were designated as MW-6, MW-7, MW-813, MW- 9, MW-10, and MW-11 (see attached maps) A seventh boring (MW-8A) was drilled to a total depth of 90 feet The first shallow boring drilled (MW-8B) was ' advanced to a total depth of 50 feet below grade while the other 5 borings were advanced to a total depth of 45 feet After MW-8B was drilled to its planed total depth of 50 feet, a groundwater measurement revealed that the level of ' groundwater was near 24 feet below grade This meant the top of the planned screened interval would be about one foot below the surface of groundwater The ' decision was made in the field to drill the remainder of the shallow borings to a total depth of 45 feet so that the screened interval would intersect the groundwater surface While drilling, all soil cuttings were placed in D O T ' approved, steel 55 gallon drums for temporary storage pending profiling and proper disposal ' In order to minimize the possibility of cross-contamination of deeper soils in the deep boring (MW-8A) with what was anticipated to be high levels of gasoline contamination from higher levels in the same boring, the drilling was performed ' in two steps First, on March 2, 1998, 15-inch diameter augers were used to drill MW-8A to a depth of 50 feet Soil samples were collected during the drilling process to assist in logging the boring and for possible laboratory analysis After ' the boring was completed to 50 feet, 8 5/8 inch i d steel casing was set and cemented to 49 feet After the cement was allowed to cure, 8 inch diameter augers were used to deepen the boring on March 5, 1998 The wooden base plug of the 8 5/8 inch conductor casing was drilled out and the boring was deepened to its total depth of 90 feet The boring had been planned to reach a total depth of ' 100 feet below grade, however, beginning at a drill depth of 80 feet, "heaving sands" prevented the collection of undisturbed soil samples and impeded drilling operations In order not to risk loosing the boring entirely, the decision was made in the field to drill the boring to a total depth of 90 feet ' 2937 Venernan Ave ,#B240 Geo-Phase Environmental Inc. Phone (209) 569-0293 Modesto,CA 95356 Fax(209) 569-0293 I