2009-03-06_REVISION - M1983141 (4)

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1 Cash M i neWaterMonitori no AddanBrown 1 ' 2.5 Surface Water 2.5.1 Occurrence Surface water is limited at the site. The site drains steeply from the ridge crest to Gold Run to the south. Cash Gulch runs immediately to the west of the mine and mine portals, while a small unnamed gulch runs immediately to the east. All hillside drainages, and Gold Run, are generally dry, with flow only ' occurring in limited reaches during or immediately after precipitation or snowmelt events. 2.5.2 Quali ' Surface water quality at the site is not frequently sampled, due to the ephemeral nature of flow in the streams. Two samples of ponded water were taken after runoff events in Cash Gulch, with the results presented in Table 1. The quality is similar to that characteristic of water from mineralized orebodies in the district (based on quality of water observed in mine voids and portals). ' 2.6 Groundwater 2.6.1 Occurrence Groundwater in the vicinity of the mine exists in a low permeability/low yield system typical of the granitic rocks of the Front Range. Yield of wells completed in the bedrock in the area is small; typically a few gallons per minute at most. The inflow to the Cash Mme, developed to 668 feet below ground ' surface, is generally less than 2 gpm. The groundwater table is shallow (approximately 50 feet below ground surface), due to the infiltration equaling or exceeding the flow capacity of the bedrock system. The groundwater table is a muted reflection of the ground surface, and intersects the ground surface in the deeper gulches and creeks. Groundwater enters the system from infiltration of precipitation, estimated at 2" per year (10% of precipitation). The piezometric surface in the bedrock in the vicinity of the mine has been estimated ' from well water levels, mine water levels, mine inflow, and computed infiltration and is presented in Plate 3. A section through the mine showing the results of modeling the current groundwater table and subsurface flow regime is also included in Plate 8. 2.6.2 Quali ' The quality of groundwater in the vicinity of the Cash Mine is variable. The general quality of groundwater in the country rock is good, as reflected in the water quality samples taken from wells upgradient of the mine. Average quality of the water taken from the deepest of the wells (MW-1) is ' presented in Table 1. Ambient groundwater quality in mineralized veins and fissures in the mining district is of substantially lower quality, generally containing concentrations of sulfate and some metals, notably iron, manganese, ' and zinc that are elevated above the country rock water. This is the water that is present in the orebody veins, and is therefore typical of the quality of water that flows into the mines. An example of this water ' quality is also provided in Table 1. ' 1601A-20061106 2