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City of Stockton Draft Amended Report of Waste Discharge(AROWD) <br /> Austin Road Landfill Work Plan <br /> ■ All casingmaterial is decontaminated b the casing manufacturer and will be delivered to the <br /> Y g <br /> site in sealed protective wrapping. If the protective wrapping has been damaged,the drilling <br /> contractor will decontaminate the casing material prior to use. <br /> ■ Casing for the well will be 2-inch diameter,PVC(per ASTM D1875)with flush-threaded joints. <br /> Screens will be continuous,machine-slotted PVC pipe with a slot thickness of 0.010 inches. The <br /> completion interval will be selected based on the criteria stated. <br /> ■ Casing centralizers will be made of stainless steel straps and clamped to the casing above and at <br /> the base of the screen to ensure plumbness and alignment of the casing. Additional centralizers <br /> will be attached to the blank casing in 50-foot increments. <br /> ■ After the well screen and casing are installed through the drill casing,the annulus around the <br /> well screens will be filled with a formation stabilizer consisting of inert Monterey silica sand or <br /> equivalent that is well rounded and sorted,with a sand size distribution based on sieve analysis. <br /> A sample of the formation stabilizer will be retained for evidence of materials used. The <br /> formation stabilizer will be placed in the annulus and brought up five feet above the top of the <br /> screen,in order to maintain an adequate barrier to prevent grout contamination of the screened <br /> interval. The filter pack will be added in measured increments and,during placement,the casing <br /> will be raised in increments less than the height the material attains as it fills the entire annulus. <br /> During placement and raising the casing,the top of the filter pack will be sounded to ensure that <br /> it does not bridge in the casing and that it is at the appropriate height as determined from the <br /> calculated volume. <br /> ■ An annular seal will be placed above the sand pack,consisting of three feet of pure bentonite, <br /> which will be hydrated according to manufacturer instructions,followed by a grout mixture of <br /> cement and bentonite to the ground surface. During material installation the drill casing will be <br /> continuously withdrawn. The cement/bentonite grout will be emplaced using a tremie system. <br /> The cement/bentonite grout will be mixed according to the following ratios: 7.0 gallons potable <br /> water,94 pounds of Type I/II Portland Cement,and 3-4 pounds pure bentonite additive, <br /> yielding 1.55 cubic feet per sack of cement. Samples of the bentonite pellets,cement,bentonite <br /> used in the grout mixture,and water used in the grout will be retained as evidence of materials <br /> used in well construction. Two pounds of the dry material,prior to mixing,and one liter of <br /> water,will be retained. <br /> ■ The screen lengths will reflect the thickness of the permeable zones encountered. Screen lengths <br /> will be 20 feet for the shallow aquifer unit extending a minimum of two feet above the water <br /> table,and 20 feet for the deep aquifer unit. <br /> ■ The surface completion will consist of a steel protective casing set 3 to 4 feet above the ground <br /> surface. Three posts,3 to 4 feet in height,will be cemented into the ground around each <br /> monitoring well. The posts will prevent damage to the well from vehicular traffic. Each well will <br /> be locked with a padlock to prevent unauthorized access. All the locking devices will be keyed <br /> alike. <br /> W:\REPORTS\STOCKTON\AUSTIN\WORKPLAN.DOC Page 7 <br />