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Instream Numeric Standards (CWQCC 33) <br />The SL7 Phase III bond release area discharges surface runoff and spoil leachate into Segments <br />13e (Sage Creek and tributaries), Segment 13i (upper Grassy Creek), and Segment 13j (lower <br />Grassy Creek) of the Yampa River in CWQCC's Region 12 of the Yampa River Basin. The <br />stream standards for Sage Creek and Grassy Creek are based on aquatic life standards. <br />SPL is required to monitor 14 of the parameters in Segment 13e, 131, and 13j per CWQCC and <br />CDRMS. A review of the statistical summary of the water quality data provided in Yoast <br />Mine's Annual Hydrology Reports and specifically for the past three years was conducted for the <br />mine's NPDES Outfalls (NPDES 10, NPDES 11, NPDES 12, NPDES 13, NPDES 14) and stream <br />sites YSSF3, YSS2, YSGF5, and YSG5. The total recoverable iron standard (1.0 mg/1), was <br />exceeded a total of six times at site YSG5 from <br />2014 to 2018 on Segment 13j. YSG5 receives <br />drainage from outfalls 010 and 01 l and over the <br />course of 2014 through 2018 no exceedance of the <br />iron standard was measured at either outfall. <br />The total recoverable iron standard (1.0 mg/1), <br />was exceeded a total of six times at site YSG5 <br />from 2014 to 2018 on Segment 13j. YSG5 <br />receives drainage from outfalls 010 and 011 and <br />over the course of 2014 through 2018 no <br />exceedance of the iron standard was measured at <br />either outfall. <br />II The total recoverable iron standard (1.0 mg/1), is <br />7 higher at site YSGF5 than at site YSG5. YSGF5 <br />receives drainage from outfalls 010 and 011 and <br />%J over the course of 2014 through 2018 no <br />exceedance of the iron standard was measured at <br />either outfall. Exceedances at the upstream <br />YSGF5 and downstream YSG5 indicate that the <br />exceedances are not likely caused by runoff from <br />Photo 4: Constructed Drainage YPM7 the site and are generally observed during <br />snowmelt runoff. On Segment 13e, the recoverable iron standard was exceeded twice at YSS2 <br />between 2014 and 2018. No exceedance occurred upstream at YSSF3 during this time frame, and <br />upstream at Ponds 12, 13, and 14, where monitoring also occurred, showed these outfalls meeting the <br />Segment 13e standard. Therefore, the exceedances are not likely caused by runoff from the Yoast <br />Mine. Exceedances at the upstream YSS3 and downstream at YSS2 indicate that the exceedances <br />are not likely caused by runoff from the site and are generally observed during snowmelt runoff. <br />The SPL includes four monitored spoil springs (YSSPGI through 4). Spoil Spring 2 (YSSPG2), <br />flows into Annand Draw and Pond 011 (NPDES 11) respectively. Due to the fact that the post - <br />mining land uses for the Yoast Mine have been approved as grazing and wildlife habitat, a review <br />of the water quality data was compared to the CWQCC surface water agricultural standards. The <br />CWQCC Regulation 31, applies to plants grown in acidic (<6.0 pH) soils. In alkaline soils, as <br />found in the Yoast permit area, a more appropriate standard for manganese is 10 mg/1. The 10 <br />mg/1 standard was not exceeded during the past five water years (2013-2018). And, no <br />Permit Number C-1994-082 Page 18 of 23 <br />