2011-08-09_REVISION - M1981185 (56)

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vicinity (within the upgradient watershed areas). For recharge to be effective in the environment presented by Southern Colorado, large areas of exposure are needed to collect runoff and snowmelt for effective recharge. It has been noted that where the La Plata River and Little Deadwood Gulch flow across more permeable formations, such as the Entrada sandstone, the streams are losing streams in that any flow upstream of the formational contacts is take up by the formation that it is crossing. Once less permeable bedrock is encountered, the streams again exhibit surface flow. The nature of the fracture lengths and aperatures of the fracturing is not well known. However, as the vast majority of the fractures are in filled with vein deposits, it is not unreasonable to speculate that there is a thin zone of fractures in the porous media adjacent to the in filled veins and that the veins themselves are relatively impermeable. Therefore, any flow from the porous media that intersects the veins, follow the vein deposits based on the potentiometric heads. When a tunnel (adit) intersects a vein, it offers a line sink for the intercepted groundwater to discharge into the tunnel probably from the enhanced permeability zone in the fractures adjacent to veins and faults. While there is no monitoring data to substantiate groundwater flow directions or actual occurrence of developable volumes of groundwater, it is not unreasonable to postulate that what flow occurs in the porous media follows topography and structural dip. Observations of occurrence of water and also staining and evidence of water inflow into the various tunnels and mines in the immediate vicinity of the Idaho and May Day Mines supports the speculation that there is only minor groundwater flow locally in the upper formations involved in the mining (Robinson, 2011). 5.0 CONCEPTUAL HYDROLOGIC SITE MODEL Small amounts of water recharge the sedimentary formations that crop out on the hillsides above the mines and in the appropriate watersheds for each mine. The portals themselves are in separate watersheds. The amount of infiltration is in general directly influenced by the amount of precipitation. In years where there is a thick, high water content snow pack, there should be more recharge expected than in dryer years. Saturated thicknesses are probably extremely thin to non - existent due to low volumes of recharge into small, isolated recharge blocks of sediment bounded by vein deposits, faults and other formations of differing permeability and porosity. What water does move into the sediments and into the fractures zones moves downgradient in general following topography until it reaches the fracture zones where it tends to follow the fractures which are frequently bounded by largely impermeable vein deposits. In applying this model, the majority of saturated flow is parallel to and along the veins and faults that are in the area and in general at higher velocities and in concentrated zones. This in turn tends to create line sinks which dewater the saturated porous media for large distances from the fracture or vein.