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Groundwater Well Installation Standard Operating Procedure SWE-FSOP-601;Revision 1 Ahtna Southwest Environmental Operations • Pump grout through a tremie pipe and fill the borehole from the bottom of the boring upward. During grouting, submerge the tremie pipe below the top of the grout column in the borehole to prevent free fall and bridging. • Add gradually to prevent bridging if bentonite solids(chips/pellets) are used. • Obtain approval of the final depth of the borehole in advance from the FTL or PL. Stop grout or bentonite addition when the general level has reached approximately one foot below the desired base of the well string (casing, screen, end plug or sump, etc.). Hydrate the bentonite plug for at least one hour before installing a filter pack. 4.3.4 Assembling and Installing Well Casing Before installation, inspect the casing, screen, silt traps, end caps, centralizers, locking covers, and any other well construction materials to confirm that no damage has occurred during shipment and decontamination activities. During the inspection,confirm that all well component materials,dimensions,and quantities are accurate before proceeding. This includes confirming that the slot size on well screens matches project specifications. If centralizers(commonly stainless steel)are used,confirm placement throughout the well string with the FTL, PL, or Field/Project geologist as appropriate. Assemble and carefully lower the well string through the open borehole,drive casing, or inside the augers until the well string is at the desired depth. Suspend the well string by the installation rig, so it does not rest on the bottom of the boring. If the well string was dropped, lowered abruptly,or for any other reason suspected of being damaged during placement, the string should be removed from the boring and inspected. In certain instances, the well string may rise after being placed in the borehole due to heaving sands. If this occurs, the driller must not place any drilling equipment (drill pipe, hammers, etc.) to prevent the casing from rising. The Field Geologist notes the amount of rise and consults with Project Geologist for an appropriate course of action. Record the following information in the FLB/notepad or field form SWE-FFRM-401, "Well Construction." • Diameter of the well boring • Total depth of well boring • Length of blank casing • Length of well screen • Length of the well end cap or silt trap • Depth to base of well string • Depth to top and bottom of well screen • Depths of centralizers, if used Page 11 of 16