Laserfiche WebLink
conducted by the applicant have demonstrated that the proposed disturbances are <br />outside of the 100 year flood plain of Munger Creek. <br />Based on monitoring data from an alluvial well at the site, the stream is not recharged <br />by an alluvial water table in the project vicinity, precluding the possibility of <br />contamination of the stream via the alluvium. The Munger Creek stream channel <br />will not be temporarily or permanently diverted [4.05.18(1)(c)]. <br />B. Diversions and Conveyance of Overland Flow <br />The collection ditches, diversions, and culverts conveying runoff from the disturbed areas at <br />the mine bench and along the Munger Canyon access and haul road will adequately carry the <br />flow resulting from the 10-year, 24-hour event. Ditches diverting undisturbed flow, and <br />conveying disturbed drainage from the coal waste disposal pile will adequately carry the flow <br />resulting from the 100-year, 24-hour event. <br />C. Sedimentation Ponds <br />A sediment pond has been approved and constructed to treat disturbed runoff from the <br />reclaimed coal mine waste disposal area (also referred to as the waste rock disposal site). A <br />plan view of the pond and associated drainage structures is depicted on Figure 2.2-6, cross- <br />section and specifications are depicted on Figure 2.2-7. The pond is an incised impoundment <br />with a design capacity of 0.75 acre feet. The design includes a 6" valved primary spillway <br />pipe installed at the maximum sediment storage level, and a riprapped open channel <br />emergency spillway at an elevation four feet higher than the primary spillway inlet. <br />D. Surface and Ground Water Monitoring <br />Surface Water <br />The surface water monitoring program is addressed in Section 2.5 of the application text, <br />parameter list is presented in Table 2.5-2, and monitoring site locations are shown on Figure <br />2.3-5. <br />Adequate baseline data indicating characteristics of water quantity and quality for East Salt <br />Creek in the vicinity of Munger Canyon and for the drainage in Munger Canyon was <br />provided in the original permit application, summarized in Section 4.5 of the application text. <br />Total dissolved solids in East Salt Creek have been noted over a range of 600 mg/1 to 10,000 <br />mg/l. Water is typically a sodium sulfate type. <br />In Munger Creek, like most semi-arid ephemeral drainages, dissolved constituents in surface <br />water often reach high levels during storm runoff. Dissolved solids measured in Munger <br />Canyon ranged from 92 mg/1 in December to 956 mg/1 in April. <br />23