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-34- <br />As pre viousZy mentioned, Salt Creek Mining Company has proposed a 25,000 cubic <br />yard underground development waste disposal site to be located adjacent to the <br />Munger Canyon Mine. This waste rock pile will cover 2.6 acres and will be 35 <br />feet high (see Section 2.2.5 of Volume I of the application). Roof fall rock <br />from both the Munger Canyon and McClane Canyon Mines, along with rock slope waste <br />rock from Munger Canyon will be disposed of in this waste rock pile. The pile <br />will be located outside of the ephemeral tributary to Munger Creek and surface <br />drainage from undisturbed areas will be diverted around the pile. Surface <br />runoff from the disturbed area will be collected in a sediment pond for treatment. <br />No springs discharge in the area to be covered by the waste rock pile. An <br />alluvial monitoring well, GW-6, is to be installed below the waste rock pile to <br />monitor the effect of the structure on alluvial ground water (see Hydrologic <br />Balance: Ground Water section of the permit document). <br />The analyses of the Cameo roof and floor strata contained in Tables 2.1-4 and <br />2.1-5, Volume I of the McClane Canyon permit application indicate that the <br />strata associated with the Cameo seam have high sodium adsorption ratios (SAR) <br />and high pH's. These conditions indicate that the material may limit revegetative <br />success on the reclaimed waste rock pile unless the pile is adequately covered <br />with non-toxic soil and rock materials. Analyses of the material to be generated <br />by the rock slope, as required in Stipulation No. 1, will indicate whether or <br />not material in the waste pile will be toxic. If these analyses indicate the <br />material is toxic, mitigation will be required, as specified in Rule 4.14.3. <br />Salt Creek Mining Company has demonstrated that the waste disposal pile will <br />be located outside of the I00-year flood plain of Munger Creek. The reach of <br />the Munger Creek stream channel in the vicinity of the proposed waste pile will <br />totally contain the IDO-year flood (based on an analysis of measured channel <br />cross-sections). <br />The reclamation plan (Map 3.I-1) indicates that Salt Creek Mining Company intends <br />to reestablish the drainage at the mine bench to approximate the pre-mining <br />configuration. An analysis of the expected velocity of flow in the drainage <br />indicated that velocities for the reestablished drainage are potentially very <br />erodible for the 100-year, 24-hour storm event (approximately 26.5 feet/second <br />in steeper reaches of the channel). The post-mining topography does not differ <br />markedly from the pre-mining topography. <br />in the pre-mining configuration, the steepest portions of the stream channel are <br />composed of a resistant rock ledge, which explains the stability of the natural <br />stream channel. When the area is reclaimed, unconsolidated material will be <br />backfilled over the original channel. The unconsolidated material would obviously <br />be less resistant to erosion than the resistant rock Ledge. <br />Because of the high erosional velocities anticipated for the post-mining configur- <br />ation, it would be advantageous to construct a permanent structure in the reach <br />of the stream that would experience the greatest erosion. For this reason, the <br />following stipulation is required by the Division: <br />