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August 1994 ES-i 933-2713.003 <br /> EXECUTIVE SUMMARY <br /> Simon Hydro-Search prepared reports in 1992 and 1993 which indicated that plugging of the <br /> American Tunnel might result in increased groundwater flow from the mine workings towards <br /> the Cement Creek drainage near the Sunnyside Gold property. Sunnyside Gold Corporation <br /> subsequently authorized Golder Associates Inc. (Golder) to complete a study of conjunctive flow <br /> in Cement Creek to determine the relative amounts of surface and groundwater flow in the <br /> creek. <br /> In order to accomplish conjunctive flow characterization, boreholes were drilled to obtain <br /> additional geologic information, piezometers were installed to monitor water levels and to allow <br /> in-situ testing of hydraulic conductivity, and laboratory testing of soil samples was conducted <br /> to provide additional hydraulic conductivity data. Seven boreholes were drilled along two cross- <br /> sections located approximately perpendicular to Cement Creek. Continuous core samples were <br /> collected to allow visual characterization of the materials and to develop a vertical profile of the <br /> sediments. The borehole drilling program yielded a sediment profile generally consisting of <br /> clayey-gravel fill near ground surface, underlain by a sandy gravel zone, with a clayey gravel <br /> layer at the base. The sandy gravel zone averages approximately 12 feet in thickness. <br /> Piezometers were installed in five of the seven boreholes and consisted of 2-inch diameter <br /> polyvinylchloride(PVC) screens and risers. Piezometers were completed using 10-feet of screen <br /> which was generally placed adjacent to the sandy gravel layer. In-situ hydraulic conductivity <br /> testing was conducted in the piezometers by introducing and subsequently removing a 1.2-inch <br /> outside diameter, variable-length, sealed PVC pipe. The water level response to 'slug' <br /> introduction and removal was monitored using a transducer and data logger capable of providing <br /> data as early as 0.2 seconds after start of the test. Slug test data were analyzed using two <br /> methods (Hvorslev, and Bouwer and Rice) which involve fitting a straight line to the data on a <br /> log-linear graph. <br /> The slug tests yield a hydraulic conductivity for the sandy gravel of approximately 5 x 10-5 <br /> cm/sec. This compares to an expected hydraulic conductivity of about 1 x 10-2 cm/sec for clean, <br /> sandy gravels and suggests that the sandy gravels in Cement Creek are not clean but rather have <br /> significant fine-grained material such as clay and silt occupying the pore spaces. During slug <br /> testing, it was noted that the piezometers had significant silt within the casing, despite the use <br /> of small slot-sizes (0.010-inch slots) for the piezometer screens and the use of sand packs. <br /> Laboratory analyses were performed to determine the vertical hydraulic conductivity of the <br /> clayey gravels encountered in the boreholes. The average vertical hydraulic conductivity of the <br /> fine-grained materials was determined to be about 3 x 10' cm/sec. The contrast of hydraulic <br /> conductivity between the sandy gravels and the underlying clayey gravels is such that the clayey <br /> gravel is expected to act as an aquitard, with the majority of groundwater flow occurring within <br /> the sandy gravel unit. <br /> Golder Associates <br />