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Streamflow could be reduced due to infiltration of runoff through <br />subsidence fractures. However, this impact has not been identified by <br />any of the monitoring programs, despite the presence of subsidence <br />features at several mines. Recharge to the mine in zones of undermining <br />may occur, The amount of recharge is related to the type of stream <br />ephemeral or perennial. Ephemeral streams experience little impact due <br />to steep stream gradient, presence of tittle alluvium, and the <br />high-intensity, short-duration nature of flow. Perennial streams, <br />however, mdy experience significant depletions of flow if mine workings <br />exist adjacent to or below the stream. The lower stream gradient and the <br />thicker alluvial deposits in perennial streams favor flow retention and <br />recharge to ground water systems. The only perennial streams which are <br />proposed to be undermined are the Dry Fork of Minnesota Creek and Lick <br />Creek. A plan for limited extraction under these streams should preclude <br />any subsidence fracturing and therefore impacts to the stream. <br />Subsidence fracturing, as a result of mining, may cause a reduction in <br />spring discharges. The potential for this impact exists in the area of <br />the Mt. Gunnison No. 1 mine. Currently, monitoring is being conducted to <br />evaluate the impact of subsidence on spring discharge and stream flow. <br />In the meantime, the mine plan has been modified to provide a buffer zone <br />associated with Dry Fork and Lick Creeks where only very limited <br />extraction will occur. In addition, a water augmentation plan is in <br />place whereby water rights impaired by spring water discharge to the <br />workings would be met with releases of other water in the Minnesota Creek <br />basin. <br />Other impacts could potentially include a decrease in the number of <br />discharge points, and a change in their location, or a decrease in runoff <br />due to increased infiltration. Geomorphic impacts could include a change <br />in channel and watershed morphology and geometry or modification of <br />erosion rates. All active mines examine their affected areas annually <br />and report on the magnitude of surface subsidence cracks when <br />encountered. While alt of these impacts are possible, they are not <br />probable. <br />o A11 the permitted mining operations withdraw water from the North Fork <br />watershed. These withdrawals could diminish streamflow. This water is <br />used during mining operations, crushing, screening, and loading of coal, <br />as wail as bathhouse use and potable water supplies. A1] the operations <br />have rights to the water they are using and many have augmentation plans <br />in place to repair any water rights which are impaired by their <br />operations. The total estimated water consumed by all of the mines <br />presently operating in the North Fork of the Gunnison drainage basin is <br />396 acre-feet per year. This amounts to approximately 0.14% of the mean <br />annual yield of the river. This indicates that coal mining activities <br />within the basin have a very minor impact on the quantity of water <br />available in the basin. <br />-13- <br />