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g f = r STANDARD OPERATING PROCEDURES RE.HOLLOW-STEM AUGER MONPCOR WELL TNSTATdA71ON AND DEVELOPMENT SOP-3 The boreholes for monitor wells are drilfed using a truck-mounted hollow-stem auger drill rig.The diameter of the bo,chole will be a minimum of four inches larger than the outside diameter(OD) of the casing when installing well screen. The hollow-stem auger provides minimal interruption of drilling while permitting soil sampling at desired intervals. Soil samples are collected by hammering a conventional split-barrel sampler containing pie-cleaned 2-inch brass sample tubes. Aeolo " t g t� from Western Geologic Resources continuously logs each borehole during dri&2r,and constantly checks drill cuttings for odors. The sampler is rinsed between samples and steam-cleaned with all other drilling equipment between borings to prevent cross-contamination. Monitor wells are cased with threaded, factory-perforated and blank Schedule 40 PVC. The perforated interval consists of slotted casing,generally 0.020-inch wide by 1.5-inch long slot size, with 42 slots per foot. A PVC cap is fastened to the bottom of the casing with stainless steel screws;no solvents or cements are used. Centering devices may be fastened to the casing to assure even distribution of filter material and grout within the borehole annulus. The well casing is thoroughly washed and steam-cleaned prior to installation. After setting the casing inside the hollow stem,sand or gravel filter material is poured into the annular space to fill from the bottom of the boring to l foot above the perforated interval. A 1- to 2-foot thick bentonite plug is placed above this filter material to prevent grout from infiltrating hf down into the filter material. Neat cement,containing about 5%bentonite,is then tremied into the annular space from the top of the bentonite plug to the surface. A lockable PVC cap is placed on m each wellhead. Traffic-rated Christy boxes are installed around the wellhead for welts in parking lots and driveways while steel stove pipes are usually.set over wellheads in landscaped areas. After installation,the wells are thoroughly developed to remove residual drilling materials from the wellbore,and to improve well performance by removing any fine material in the filter pack that can pass from the formation into the well. Well development techniques used include pumping,bailing, surging,swabbing,jetting,flushing,and airlifting. All development water is collected in 55-gallon drums for temporary storage,and is then disposed of properly depending on analytic results. To assure that cross-contamination does not occur between wells during drilling and development,all t development equipment is steam-cleaned. Y� - i u