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------ ------ _...............................__...__...... _.. ..................... <br /> casings. Once installation has begun,work will continue until the well has been <br /> grouted and the drill casing has been removed. <br /> • Well screens,casings,and fittings will conform to National Sanitation Foundation <br /> Standard 14 or American Society for Testing and Materials(ASTM)equivalent for <br /> potable water usage. Material used will be new and essentially chemically inert to the <br /> site environment. <br /> • Filter pack will extend from the bottom of the screened section (top of aquitard)to a <br /> height of 2 ft above the top of the screen. If the water table is relatively close to the <br /> ground surface,the filter pack may extend less than 2 ft above the screen to avoid <br /> surface water infiltration into the well and to allow for placement of the bentonite <br /> seal,grout,and protective casing. If the hole is less than 20 ft deep,the filter pack <br /> may be poured into the annulus directly. If the hole is deeper than 20 ft,the filter <br /> pack must be tremied into place. <br /> Granular filter packs will be chemically and texturally clean,inert, and siliceous. <br /> - Filter pack grain size will be based on formation grain-size analysis. <br /> — Calculations regarding filter pack volumes will be entered into the Field Logbook <br /> along with any discrepancies between calculated and actual volumes used: If a <br /> discrepancy of greater than 10 %exists between calculated and actual volumes, an <br /> explanation for the discrepancy will also be entered in the Logbook. <br /> • Bentonite seals will be no less than one foot or more than three feet thick as measured <br /> immediately after placement. <br /> • Grout <br /> Grout used in construction will be composed by weight of approximately: <br /> 20 parts cement(Portland cement,type 11) <br /> 0.6 to 1 part(max.)(3-5%)bentonite=2.8 lbs to 4.7 lbs of bentonite to one 94 lb <br /> bag of cement <br /> — 6.5 gallons approved water per 94-1b bag of cement: <br /> Neither additives nor borehole cuttings will be mixed with the grout. Bentonite will <br /> be added after the required amount of cement is,mixed with the water. <br /> • All grout material will be combined in an above-ground container and <br /> mechanically blended to produce a thick, lump-free mixture. Mixing of the grout <br /> will be performed by mixing the bentonite powder and water before adding <br /> Page 6 of 9 <br /> well-install_SOP MONITORING WELL INSTALLATION February 2005 <br />