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Homestake 2011 Geotechnical Observations Pitch Reclamation Project Indian Creek and Tie Camp Creek Waste Rock Dumps levels recorded over the previous few years were from a small interval of water perched on the silt in- filling, and because of the blockage in the standpipe, not indicative of water levels in the underdrain. In 2010, water levels in this IC10300 were once again sporadic and required additional high pressure flushing to push through the silt built up in the casing. In the 2010 report it was noted that this piezometer may have reached a point where it no longer provided accurate information of the phreatic surface in this portion of the rock dump. It was decided that piezometers IC10300 and IC10370 would be replaced in 2011 to allow more accurate measurement of the phreatic surface in this portion of the Indian Creek rock dump. In August 2011, both piezometers IC10300 and IC10370 were sealed and were replaced with two new piezometers at approximately the same locations. Piezometer IC10300 was abandoned during well completion of IC10300R. Prior to abandonment, the well had an existing depth of 189.5 ft bgs and a static water level at 187.3 feet bgs. Abandonment included backfilling the piezometer with sand from 163 to 189 feet bgs, hydrated bentonite chips from 135 to 161 feet bgs, and a high solids bentonite grout from 0 to 135 feet bgs. A back -hoe was employed to dig out and remove the top 6 ft of well casing and the excavation then backfilled. Similarly, piezometer IC10370 was abandoned during well completion of IC10370R. Prior to abandonment, the well had a depth of 185.5 ft bgs and did not have a measurable static water level. Abandonment included backfilling the piezometer with sand from 68 to 185.5 feet bgs, hydrated bentonite chips from 34 to 68 feet bgs, and a high solids bentonite grout from 0 to 34 feet bgs. A back -hoe was used to dig out and remove the top 6 feet of well casing, the excavation was then backfilled. The replacement piezometer IC10300R was located approximately 30 feet to the west of the former location of IC10300. The borehole was spudded on August 25, 2011. Drilling progressed regularly through predominately silty, gravelly, and boulder -sized waste rock material. The borehole was terminated at a depth of 210 ft. Well construction was completed with a 20 feet screen. Sand pack consisted of 90% silica NSF -61 grade filter pack. A hydrated bentonite plug was set above the filter pack and a high solids bentonite (.20% bentonite by weight) grout was emplaced above the bentonite plug. The wellhead was completed with concrete and an 8 -inch steel well protective casing and concrete apron. Compressed air was used for drilling to a depth of 178 ft bgs, at lower depths, water injection was employed to remove gravel from the casing and to ensure good return of cuttings. Piezometer IC10370R was located approximately 67 feet to the west of the former location of IC10370. The borehole was spudded on August 27th, 2011. Drilling progressed regularly through predominately silty, gravelly, and boulder -sized waste rock material, similar to waste rock encountered at IC- 10300R. Compressed air was used for drilling to a depth of 85 ft bgs. At lower depths, water injection was employed to remove gravel from the casing and to ensure good return of cuttings. The borehole was terminated at 208 ft bgs. Well construction was completed with a 10 feet screen centered in the borehole. The sand pack was set using 90% silica, NSF -61 sand to approximately 11 ft above the loss -of- return depths. A hydrated bentonite plug was set above the sand pack. A high solids bentonite grout was emplaced above the Homestake Pitch Reclamation Project 2011 Annual Geotechnical Report M- 1977 -004HR Page 3 December 19, 2011 2011 AnnualGeotechnicalReportText _Final.doc