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Colowyo, C1981 -019, PR3 adequacy No. 3 18 July 22, 2011 <br />Gulch. Please expand the permit text narrative regarding the potential for spoil water discharge <br />and impacts to downstream areas. <br />Please revise the prediction of spoil spring discharges to the surface for the Collom Lite Pit to <br />reflect the requested re- calculation of annual pitwall seepage. <br />No further response is needed for this comment, as pihvall seepage in Collura Lite pit is <br />addressed elsewhere in this letter. <br />3. As mentioned previously, the plan for control of surface water drainage through the disturbed <br />area is deficient at this time due to uncertainty of the proposed mine plan and the long -term <br />presence of the temporary spoil pile in the center of the disturbed area. The application does <br />not adequately present how surface water will be handled over the life of the operation (Rule <br />2.05.6(3)(b)(i)). <br />The response is inadequate. The application does not adequately present how surface water <br />will be handled over the life of the operation (Rule 2.05.6(3)(b)(i)). The Division cannot defer <br />sediment control issues to a later date unless CCC is requesting only limited mine plan <br />approval for the Collom Lite and Little Collom X areas. The Division understands the worst <br />ease scenario for hydrology and sedimentology and has specific questions related to that review <br />later in this letter. CCC states in response to this question, "Later stages in the mine <br />progression will be reviewed in more detail..." That detail is required for all areas within the <br />Collom proposed permit area in the current revision application (PR -03). Please refer to the <br />original question. <br />Please reterto question 2.05.314) above. <br />4. Please revise the third paragraph on page 132 to reflect the prediction that there will be limited <br />discharge into the pitwalls. <br />"this item k adequate. <br />5. Please use in the calculations of spoil resaturation time a spoil recharge rate, rather than a <br />bedrock recharge rate. A reasonable spoil recharge rate for the Collom area would be 3.1 <br />inches per year, calculated as 18% X 17 inches per year average precipitation. The 18% factor <br />is based on Williams and Clark's (1994) spoil lysimeter study which found that approximately <br />18% of annual precipitation recharge spoil at a Remit County mine. The annual recharge <br />values used in the submittal (0.2 to 0.35 inches, and 1.1 inches) are less than 7% of annual <br />precipitation in the Collom area and apply to undisturbed bedrock, whose permeability, and <br />consequently annual recharge, would be a fraction of the value for spoil. <br />Al previously requested. please use in the calculations of spoil saturation time a reasonable <br />surface infiltration rate into Collura Lite spoil of 3.1 inches per year, calculated as Is",, X 17 <br />inches per year average precipitation. In order a, reflect (lie ',.I inches per year infiltration, <br />please change the 0.016 efs value on page 133 to 031 cfs, and change the 0.75 inches per year <br />recharge rate at the bottom of page 136 to 3.1 inches per year. <br />