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RULE 4 PERFORMANCE STANDARDS <br />4.05 HYDROLOGIC BALANCE <br />4.05.1 General Requirements <br />Please see Section 4.05.1 in Volume 1. <br />In addition to the mining, reclamation, and treatment methods referenced in this Section, further protection of <br />the hydrologic balance will be established by an on-going plan for monitoring potential changes in surface <br />water quality and quantity and groundwater quality. This monitoring plan is described in Volume 15, Section <br />4.05.13 and the monitoring locations are graphically shown on Map 1013. Excess spoil valley fill areas are <br />located up -dip from mining and reclamation areas and periodic monitoring for seeps and springs and periodic <br />monitoring of piezometer wells will detect the formation of spoil springs. <br />4.05.2 Water Quality Standards and Effluent Limitations <br />Please see Section 4.05.2 in Volume 1. <br />4.05.3 Diversions and Conveyance of a Watershed Less than One Square Mile <br />The drainage and sediment control measures described under Section 2.05.6 and presented in Erosion and <br />Sediment Control Structures (Exhibit 7, Item 20) provides for temporary diversion of surface drainages within <br />the permit area. A system of temporary ditches will be used to divert runoff from disturbed areas to sediment <br />ponds. Temporary diversions will be constructed to pass at a minimum the runoff from the precipitation <br />event with a two-year recurrence interval. <br />The temporary diversions drain watersheds less than one square mile in size and serve to reduce the <br />contribution of suspended solids to runoff. The diversions will be constructed with a minimum gradient to <br />pass the design flow and will be stabilized with grasses or riprap. If not removed by mining, upon completion <br />of mining and at an appropriate point mandated in the Coal Regulations of the Colorado Mined Land <br />Reclamation Board, the temporary diversions will be reclaimed as required in Section 4.05.17. <br />The only stream channels that will be impacted by the South Taylor pit are headwaters tributary to Taylor <br />Creek and West Fork Good Spring Creek, which are intermittent and drain watersheds less than one square <br />mile. There will be no upstream diversions of these streams since mining will extend to the top of the <br />drainages. The headwaters systems will be restored to historic drainage patterns once temporary diversion <br />ditches are removed; therefore, there will be no permanent diversions of these channels. <br />4.05.4 Stream Channel Diversions (Relocation of Streams) <br />No diversions of perennial streams or streams that drain watersheds that are greater than or equal to one <br />square mile in size are planned or provided for at this time. The stream channels of Good Spring and Wilson <br />Creeks will be maintained in their natural positions. <br />South Taylor/Lower Wilson — Rule 4, Page 3 Revision Date: 4/7/17 <br />Revision No.: RN -07 <br />