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Groundwater Well Installation Standard Operating Procedure SWE-FSOP-601;Revision 1 Ahtna Southwest Environmental Operations 4.2.3 Mobilization Once the site is prepared, the rig is mobilized and located over the borehole. • The drill rig is mobilized to the site and located over the borehole location • The drill rig is leveled with a set of hydraulic pads attached to the front and rear of the drill rig • The driller should always raise the mast slowly and carefully to prevent tipping or damaging the rig and avoid obstructions or hazards 4.3 Well Installation Procedures 4.3.1 Drilling The following procedures assume that the drilling of the borehole occurred per the project work plan and appropriate SOPS (see SWE-FSOP-300 Series [various drilling methods]). During fieldwork,the Field Geologist will generally: • Observe and monitor rig operations • Conduct all health and safety monitoring and sampling, and supervise health and safety compliance 4.3.2 Borehole Preparation At total depth, remove soil cuttings through circulation or rapidly spin the augers before constructing the well. Review logs and notes with the driller for any zones or depths exhibiting drilling problems that may affect the well installation. Condition the hole or take other actions mutually agreed upon by the Field Team (FTL, PL, Field/Project geologist, driller)to aid in the well installation. Remove the drill pipe and bit if using rotary techniques, or remove the center bit if using the hollow stem auger technique. Install the well construction materials inside the open borehole or through the drive casing or augers center. Measure the total depth of the completed boring using a weighted sounding line. The borehole depth is checked to assure that formation material has not heaved to fill the borehole. If heaving has taken place, discuss cleaning, re-drilling, or installation options in the open section of the boring with the Field Team (FTL, PL, Field/Project geologist, or driller). 4.3.3 Grouting Overdrilled Boreholes If the hole was over drilled to a depth greater than needed for well installation, backfill material such as grout, bentonite pellets, or bentonite chips (as specified in the project work plans) may be added to the bottom of the boring to raise the bottom of the hole to the desired depth. • Before placing materials, confirm the borehole dimensions and calculate the estimated volume of material required, including allowances for hydration of dry materials. • Closely monitor the progress of borehole backfilling by frequently tagging the level in the borehole and comparing against estimated fill quantities.This is especially important if irregularities in the borehole are suspected (e.g.,voids, sloughing). Page 10 of 16