Laserfiche WebLink
Mine Discharge Monitoring <br />Mine Water Pumping Sites - Underground mine water is pumped at two locations, Site 109 and Site 115. Site 109 <br />is located near the main portals. Water pumped from 109 can either be discharged to Foidel Creek (via Pond D or <br />F), or be used underground. Table A specifies sampling requirements for Site 109 discharges. Site 115 (FCB <br />Treatment Facility), which dewaters the majority of the mine, is located northwest of the main portals. At Site 115, <br />water that collects in the downgradient sealed mine workings is pumped to the surface, where it is passes through <br />the water treatment facility. The treated discharge from Site 115 is then channeled to Fish Creek. NPDES/CDPS <br />Permit CO -0042161 establishes the frequency of monitoring and effluent limitations for Site 115. Flow meters <br />monitor the quantity of mine discharge at both pumping sites. <br />Purpose of Monitoring Pumped Water - An important objective of monitoring at Sites 109 and 115 is to assure <br />compliance with Trout Creek's 250 mg/1 in -stream sulfate standard. This standard applies year-round to Trout <br />Creek below Fish Creek, and applies June through February to the segment of Trout Creek between Middle and <br />Fish Creeks. Site 115 monitoring has the additional objective of meeting the 1,500 umhos/cm material damage <br />standard for conductivity set by DMG on Fish Creek. As described below, mine pumping at Sites 109 and 115 is <br />varied to prevent excessive chemical loading of Fish Creek and Trout Creek. Maximum discharge rates for Site <br />115 is determined by regularly entering monitoring data into two series of stream -loading calculations called the <br />"Fish Creek Calculator" and the "Mine Discharge Calculator". Separate loading calculations are made to determine <br />the maximum discharge rate for Site 109. <br />Conductivity as a Sulfate Indicator - Since it is difficult to accurately measure sulfate levels in the field, <br />conductivity has been used as the indicator parameter for sulfate. In Exhibit 32, at the Station 69 node, the dry <br />season TDS and sulfate levels were modeled to be 412 and 174 mg/l respectively. Using the conversion factor of <br />0.75, TDS is equivalent to a conductivity of 549 µmhos/cm. The ratio of the sulfate to conductivity levels is <br />estimated to be 0.32. The current stream standard of 250 mg/L is therefore equivalent to a conductivity of 780 <br />µmhos/cm. TC selected 750 µmhos/cm to use in its calculator, as a conservative standard. Additional data may be <br />used to correlate EC with sulfate in the future, in which case, a new EC value could be developed for use in the <br />calculator. <br />Monitoring and Loading Calculations for the 250 mg/1 Trout Creek In -Stream Sulfate Standard - The <br />"Contingent" monitoring in Table A includes monitoring aimed at preventing exceedances of the 250 mg/l sulfate <br />standard for Trout Creek. As described below, the monitoring varies depending on which underground pumping <br />sites are discharging. <br />Only Site 115 discharging - Weekly flow and EC data will be obtained from Sites 69, 115, <br />and 1003, and EC from Site 1005, and then will be entered in the "Mine Discharge <br />Calculator" (see Table E49-26). The Mine Discharge Calculator is used to determine the <br />maximum discharge rate for Site 115 that will not cause an exceedance of the 250 mg/l <br />sulfate standard for Trout Creek. For example, if the electrical conductivity at Sites 1003 <br />and 1005 is more than 750 µmhos/cm, TC would not be able to discharge because the <br />sulfate limit is already being exceeded (based on the 0.32 conductivity to sulfate <br />relationship, described above). TC will continue to review the EC/sulfate relationship and <br />may modify the EC value to reflect this review. In the event that the electrical conductivity <br />is below 750 µmhos/cm, then the evaluation would be made as to the rate at which effluent <br />can be discharged to Fish Creek and maintain compliance with the sulfate standard on <br />Trout Creek. The winter flow estimates will be as described below for Sites 69 and 1003. <br />Only Site 109 discharging - Between June and February, when only Site 109 is <br />discharging and the discharge is entering Foidel Creek, weekly monitoring will be <br />performed at Site 69 for flow rate and conductivity, and at Site 301 for conductivity. This <br />data will be used for calculating the maximum rate of discharge from Site 109. <br />RN 12-06 Exhibit 14 - 3 04/01/13 <br />