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PERMFILE52147
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PERMFILE52147
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Last modified
8/24/2016 10:56:02 PM
Creation date
11/20/2007 3:13:53 PM
Metadata
Fields
Template:
DRMS Permit Index
Permit No
C1982056A
IBM Index Class Name
Permit File
Doc Date
5/21/2004
Section_Exhibit Name
Exhibit 14 Hydrology Monitoring Plan
Media Type
D
Archive
Yes
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• Rating Curves for non-USGS Stream Flow Stations. Flow measurements will be determined from stage <br />readings recorded for a transect at each station and its corresponding rating curve. The rating curve for each <br />station will be determined twice annually, once in the late spring or eazly summer, and once in the fall. If rating <br />indicates the need for a new rating curve, then more frequent stream ratings will be performed. <br />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 <br />or F), or be used underground. Table A specifies sampling requirements for Site 109 discharges. Site 115 (FCB <br />Treatment Facility) is located northwest of the main portals; it dewaters the majority of the mine. At 115, water <br />collects in sump rooms and is then pumped up to the surface where it is passes through the water treatment <br />facility. The discharge from 115 is then channeled to Fish Creek. IdPDES Permit CO-0042161 establishes the <br />frequency of monitoring and the effluent limitations for 115. Flow meters monitor the quantity of mine dischazge <br />at both pumping sites. <br />Purpose of monitoring pumped water. An important objective of monitoring at Sites 109 and 115 is to ensure <br />compliance with Trout Creek's 250 mg/1 instream sulfate standard. This standard applies year-round to Tmut <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 1500 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. Site 115's maximum pumping rate <br />is determined by regulazly entering monitoring data into two series of stream loading calculations called the "Fish <br />Creek Calculator" and the "Mine Discharge Calculator". Separate loading calculations are made for determining <br />Site 109's maximum dischazge rate. <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, a[ the Station 69 node, [he dry <br />season TDS and sulfate levels were modeled to be 412 and 174 mg/1 respectively. Using the conversion factor <br />of 0.75, TDS is equivalent to a conductivity of 549 umhos/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 />umhos/cm. TCC selected 750 umhos/cm as a conservative standard to use in its calculator and this is considered a <br />conservative estimate. Additional data may be used to correlate EC with sulfate and a new EC value could be <br />used in the calculator . <br />Monitoring and loading calculations for Trout Creek's 250 mgA instream sulfate standard. The "Contingent" <br />monitoring in Table A includes monitoring aimed at preventing exceedances of Trout Creek's 250 mg/l sulfate <br />standard. As described below, the monitoring varies depending on which underground pumping sites are <br />discharging. <br />Only Site 115 discharging - Weekly flow and EC data will be obtained from Sites 69, <br />115, and 1003, and EC from Site 1005, and then will be entered in the "Mine Dischazge <br />Calculator' (see Table E49-26). The Mine Discharge Calculator determines Site 115's <br />maximum discharge rate that will not cause an exceedance of Trout Creek's 250 mg/1 <br />sulfate standard. For example, if the electrical conductivity at Sites ]003 and 1005 is <br />• more than 750 umhos/cm, then TCC would not be able to discharge because the sulfate <br />limit is already being exceeded (based on the 0.32 conductivity to sulfate relationship, <br />described above). TCC will continue to review the EC/sulfate relationship and may <br />• modify the EC value to reflect this review. In the event that the electrical conductivity is <br />PR 04-06 Exhibit 14 - 3 5/03/04 <br />
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