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• <br /> 3 foot lifts prior to retraction of the augers. A minimum of 0.5 foot of filter pack shall remain in <br /> the augers at all times during filter pack installation. Frequent measurements shall be made inside <br /> the annulus during retraction to ensure that the filter pack is properly placed. Volume of filter <br /> pack used vs. elevation of filter pack shall be noted to determine if bridging is a problem. <br /> The filter pack material for all wells will be placed to an elevation of three feet above the top of <br /> the well screen. Upon reaching this interval, the material will be surged for at least 15 minutes <br /> with a surge block appropriately sized for the inside diameter of the well and allowed to settle for <br /> a minimum of 20 minutes. If necessary,additional filter pack material will be placed into the hole <br /> and the surging procedure repeated until the specific top of sand elevation has been obtained. <br /> 3.3.6 Bentonite Seal <br /> After the final placement of the filter pack material,a 6-inch lift of fine mesh sand(size#70) will <br /> be placed on top of the filter pack. The purpose of the sand is to protect the filter pack material <br /> during the placement and compaction of the bentonite seal. <br /> A minimum 3 foot thick and not more than 5 foot thick hydrated bentonite seal, installed to <br /> protect the filter pack during grout placement, shall be placed on top of the fine mesh sand in a <br /> manner which prevents bridging of the bentonite in the annulus. The top of the bentonite seal <br /> shall be a minimum of 3 i/s feet above the top of the filter pack. The depth to the top of the <br /> bentonite seal shall be directly measured, and recorded immediately after placement, without <br /> allowance for swelling. <br /> If the bentonite seal is to be placed into unsaturated conditions,bentonite pellets or chips will be <br /> placed into the annular space just above the fine mesh sand and hydrated with distilled water in <br /> place. If the bentonite seal is to be placed in saturated conditions (i.e.,below the water table), the <br /> bentonite pellets or chips will be placed onto the top of the fine mesh sand in a manner so as to <br /> prevent bridging of the pellets in the annular space. The pellets will be allowed to hydrate in <br /> accordance with the manufacture's recommendations prior to grout placement. <br /> 3.3.7 Grout Placement <br /> A non-shrinking cement grout,shall be mechanically mixed in accordance with paragraph 2.5 <br /> CEMENT AND BENTONITE GROUT, and placed in one continuous operation into the annulus <br /> above the bentonite seal to the ground surface. Grout injection shall be in accordance with <br /> ASTM D 5092. The tremie pipe shall be thoroughly cleaned with high pressure hot water/steam <br /> before use in each well. The bottom of the tremie pipe shall be constructed so as to direct the <br /> discharge to the sides rather than downward. The discharge end of the tremie pipe shall be <br /> submerged at all times. Additional grout shall be added from the surface to maintain the level of <br /> the grout at the land surface as settlement occurs. No work shall be conducted in the well within <br /> 24 hours after cement grouting. The alignment of the well shall be verified by passing a 5 foot <br /> 02671-008 <br />