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~. WORST CASE WATER QUALITY IMPACT EVALUATION NORTH FORK OF THE GUNNISON RIVER MINE WATER DISCHARGE AT 2,000 GPM Parameter Jul. Au Se t. Oct. Nov. Dec. Mine Dischar e Flow (cfsl 4.46 4.46 4.46 4.46 4.46 4.46 iDS Img/II 4.285 4,285 4,285 4,285 4,285 4,295 CI Im ll) 664 664 664 664 664 664 Fe (Total Recoverable, m /II 0.89 0.89 0.89 0.89 0.89 0.89 Fe IDissolved, m /II 0.06 0.06 0.06 0.06 0.06 0.06 Na (m /II 1,700 1,700 1,700 1,700 1,700 1,700 North Fork Dischar e Flow (cfsl 65 60 60 60 60 60 TDS (m 111 108 108 108 108 109 108 CI (m /II 3 3 3 3 3 3 Fe (Total, m lIl 1 .7 1.7 1.7 1.7 1.7 1 .7 Fe IDissolved, m /II 0.08 0.08 0.08 0.08 0.08 0.08 Na Im /II 8.4 8.4 8.4 8.4 8.4 8.4 Cumulative Discharge Flow Icfsl 70 65 65 65 65 65 TDS Im /II 373 394 394 394 394 394 C11m !II 45 48 48 48 48 48 Fe (Total, mg/II 1.63 1.63 1.63 1.63 1.63 1 .63 Fe (Dissolved, m /II 0.08 0.08 0.08 0.08 0.08 0.08 Na lm /II 116 124 124 124 124 124 Notes: 11 Mine discharge water quality based on analysis of sample 15/19/99) from Pond E with TDS of 4,285, CI of 664, Fe (Total recoverable) of 0.89. Fe (Dissolved) of 0.06, and Na of 1,700 (all values in mg/II - It should be noted that at the 2,000 gpm discharge rate, mine water will pass through OMI's existing 7.0 to 10.0 MM gallon underground sump and mine water handling system which will reduce both TSS and TDS 21 North Fork flows from USGS Database for North Fork Gunnison River Near Somerset (Period of record 1934 through 1998, values are minimum daily flows unless flow value is less than 60 cfs which is minimum in-stream tlow maintained through control of Paonia Reservoir discharge) 3V North Fork water quality from USGS Database for North Fork Gunnison River Near Somerset (Period of record 1978 through 1998) using mean values as follows: TDS - 108, CI - 3, Fe (Total) - 1 .7, Fe IDissolved) - 0.08, and Na - 8.4 (all values in mgl1V 41 The CDPHE receiving water standards for the North Fork are CI - 250, Fe ITotall - 1.0, and Fa IDissolved) - 0.3 (all values in mg/II -Note that while the cumulative value for total iron is above the standard, baseline for the North Fork Is above the standard and mine water discharge will actually lower total Iron slightly 51 The DMG's material damage guidelines are TDS - 2501500 IdomesticlaBricultural), C1 - 250, and Fe (Total) 1 .0 - It should be noted that these guidelines are below the limits set by the EPA (Quality Criteria for Water)