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-45- in these ephemeral streams are concentrated in periods of snowmelt and high intensity precipitation events. The stream gradients are steep and their channels contain little alluvium. For all of the above reasons, very little surface water is retained long enough in the stream valleys to infiltrate into the ground water systems. Therefore, the amount of water observed reaching the mine workings is insignificant. Perennial streams, however, may experience significant depletions of flow if mine workings are extended adjacent to and/or below the level of the stream valley (e.g., the bedrock alluvial contact). The lower stream gradient and the thicker alluvial deposits in perennial stream valleys favor flow retention and recharge to the ground water systems. Due to the increased flow retention and ground water recharge in perennial stream valleys, there is a greater potential for stream depletions by mining adjacent to or under these stream valleys. The mine could generate depletions by increasing mine inflows in the area. These mine inflows could be induced either through the mine workin s encountering existing faults or fractures or strata recharged by the stream, or through the mine producing subsidence fractures which extend to the stream valley bottom or to rock strata recharged by the stream. The Somerset operation will undermine a perennial stream, and one mining operation, Blue Ribbon will be mining adjacent to a perennial drainage tributary to the North Fork of the Gunnison. Both the Blue Ribbon and the Somerset mines have surface facilities and underground mine workings located in the Hubbard Creek Drainage. The combined mining operations of the Blue Ribbon and Somerset mines may impact the quality of surface water flowing in Hubbard Creek and in the irrigation ditches supplied by Hubbard Creek. The quantity of flow may be depleted through the dewatering of faults, fractures and rock strata which are in direct or in indirect communication with the alluvium or stream bottom of Hubbard Creek. The Somerset Mine has mined beneath Hubbard Creek. Inspection of the underground workings by CMLRD hydrologists showed this portion of the mine to be making significant amounts of water. At the present time it is uncertain whether or not surface flows are being depleted. However, there is a~greater concentration of inflows and increased discharges associated with the inflow in the Somerset mine workings below Hubbard Creek. The Mt. Gunnison application proposed a subsidence protection plan for the Dry Fork of Minnesota Creek to protect streamflow. The adequacy of this protection plan was not assessed as a part of the Mt. Gunnison Mine permit review (this area lies outside of the current five year permit area). The Division stipulated that site-specific monitoring data concerning subsidence and its hydrologic effects be taken into account in the design of any protection plan.