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• 4.6.1.3.4 <br />In order to handle the non-compliance discharge, Minrec combined <br />the discharge from the No. 3 Mine, (Outfall 007), with the <br />discharge from the No. 1 Mine, (Outfall 001), as provided for in <br />its discharge permit. A 4" diameter pipe has been installed to <br />convey the discharge from Outfall 007 to the long pond. The <br />discharges from the mines were combined effective August 11, 1995. <br />All of the discharge water from the No. 3 Mine was combined with <br />the Discharge from the No. 1 Mine. <br />The mine water is treated at the No. 1 Mine by three passive water <br />treatment ponds. Two treatment ponds (T-1 b T-2) were constructed <br />during 1988. These ponds were used in combination with a chemical <br />injection system that increased the pH of the mine effluent. <br />During September 1989 a third settling pond was constructed on site <br />to handle the No. 1 Mine water. The new pond is referred to as the <br />long pond. The additional settling time provided by the long pond <br />is adequate to allow the iron to settle from the mine water and be <br />in compliance for discharge into North Thompson Creek. No chemi- - <br />cals have been added to the mine water since the long pond was put <br />in service. The long pond has worked very effectively. Cattails <br />• and algae have flourished in the long pond an have undoubtedly <br />enhanced the treatment process <br />The impact of the mine discharge can be evaluated based upon the <br />data recorded for upstream North Thompson Creek water quality. <br />Table 4.6.1.3-2 presents measured instream water quality data. <br />Suspended solids comply with the Discharge Permit limitations <br />except for one interval. One-half of the instream samples indicate <br />suspended solids measured downstream less than the upstream <br />measurement. <br />One possible explanation is that at the upstream site, the stream <br />velocities are higher because of stream morphology. The morphology <br />at this site is a narrow channel with a steep gradient. These <br />conditions cause high velocities and enable the stream to carry <br />more suspended solids. At the downstream site, the stream <br />morphology has sufficiently changed to lower the stream velocity. <br />The stream morphology has a lower gradient with a wide channel. <br />Because of the lower velocity, the stream loses some of its ability <br />to carry suspended solids and the larger particles settle out <br />first, causing the lower downstream values. <br />• 4-llla Rev. 04-13-96 <br />