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� I Setting the casing inside the hollow-stem auger, sand or gravel filter pack material is poured into the annular space to fill from boring bottom to generally one foot above the perforated inten,al. The filter pack material in the well is selected to permit the development of a zone of higher hydraulic conductivity adjacent to the well screen but not allow piping of the finer-grained formation materials into the well. The slot size of the well screen is selected so that it will retain a minimum of 45 percent of the filter pack material. Before placement of the bento ite plug, the well is surged to set the filter pack. After surging, the top of the filter pack is measured and, as necessary, additional filter pack material is added. The well is then surged again. This procedure is repeated until the filter pack will notsettle further. After setting the filter pack,a one to two foot thick bentonite plug is set above the filter pack to prevent gro t from infiltrating into the filter pack. A regulatory approved annular filling material such as neat cement, cement with fi e percent(by volume)bentonite or sand-cement grout will be used to fill the annulus from the bentonite plug to within one fbot of the ground surface. The annular filling material is placed by a method approved by the regulatory agency overseeing the site. The remaining foot of the well will be completed using a traffic-rated vault that is installed around each wellhead for wells located in parking lots or driveways, while steel (or other material) "stovepipes" are usually set over wellheads in landscaped areas. A traffic-rated vault is typically set 112-inch above grade to minimize surface water from entering the vault. In areas that may be plowed for snow removal,the vault is set flush with the surface to prevent damage to th vault by a snowplow. After completion, the well is thoroughly developed to remove residual drilling materials from the wellbore, and to improve well performance by removing fine material from the filter pack that may pass into the well. Well development techniques used may include pumping, surging, bailing, swabbing,jetting, flushing and airlifting. All development water is collected either in drums or tanks for temporary storage and is properly disp sed of depending on laboratory analytical results. To minimize the potential for cross-contamination between wells,all development equipment is either steam cleaned or properly washed prior to use. At the request of the client, and approval of the regulatory agency,the well may be developed before placement of the bentonite plug and annular seat. Soil Cuttines From Drilling Operations Soil generated during drilling operations is placed in DOT rated 55-g llon drums and stored on-site. The soil remains on-site until the proper method for disposal is assessed. Sampling Soil Cuttings Sampling of the soil cuttings is performed under the direction of a re istered geologist or civil engineer. Prior to collecting soil samples, Delta personnel will measure and calculate the volume of soil in the drums. Soil samples are typically collected from 0.5 to two feet below the surface of the drum. In some instances, two to four soil samples may be collected from each sampling interval and composited into one prior to laborat ry analysis. The soil samples are collected in cleaned, brass or stainless tubes of varying diameter and lengths (typically tv o x six inches) or other appropriately cleaned sample