PERMFILE137697

• Permit No: C1980007A
• IBM Index Class Name: Permit File
• Doc Date: 4/8/2005
• Doc Name: pages 2.05-157 to 2.05-267
• Section_Exhibit Name: 2.05 Operation and Reclamation Part 3
• Media Type: D
• Archive: Yes

Wes! Etk Mine
• Although MCC's increases for total iron appear noteworthy, inspection of the data
• indicates that these increases are not significant. During the two months that there were
stream standard exceedances for iron (March and April) even the ambient water quality
upstream from the mine exceeded the stream standard of 1.0 mg/L. Table 54 shows
that MCC's contributions to downstream total iron concentrations during March were
negligible (1 percent). In April, MCC discharges actually reduced the downstream
total iron concentration in the North Fork.
The largest total iron increase occurred in July, when the river upstream was 0.13
mg/L and downstream from the mine was 0.17 mg/L. While this calculates to a high
percentage increase, the absolute increase was of no practical significance and the
resulting concentration was well below the stream standard.
• MCC's 1996 discharges to the North Fork did not affect the pH of the river.
• In addition to reviewing the water quality data for actual discharge events during 1996,
WWE considered a "worst case" scenario in order to project future PHC's associated
with mine discharges. The worst case scenario assumes the rare situation of: (1) both
ponds discharging simultaneously, as occurred in March 1996, and (2) winter low flow
conditions in the North Fork. Even under these extreme circumstances, where the
discharge flow comprises nearly one quarter of the downstream flow, the mixed total
iron concentration is still less than the stream standard. Also, the mixed TSS
• concentration of 21 mg/L is well within the natural variability of TSS in the North
Fork. The pH was unaffected by pond discharges under the worst case scenario. This
worst case scenario also considered the effects of the increase in the TDS concentration
on crops during the irrigation season, which is discussed in more detail in the following
section.
Impact of TDS on the North Fork
TDS levels in the North Fork are elevated under natural conditions. For example, in April
1996, the TDS concentration in the North Fork upstream from the mine was 316 mglL;
MCC's discharges increased the TDS concentration to 319 mg/L (based on mass balance
computations, see Table 54).
As shown in Table 54, all of the TDS concentrations downstream from the mine were below
any numeric standards for TDS that WWE has been able to locate, irrespective of the
beneficial use classification that is to be protected (Table 55). For comparison, the highest
TDS concentration calculated downstream of the mine during 1996 was 319 mg/L. Even
under the worst case scenario, the downstream TDS concentration was calculated to be 426
mg1L (see Table 54), less than the most stringent limit shown in Table 55 (450 mg/L).
Under the worst case scenario, as shown in Table 54, the downstream mixed TDS
• concentration would be approximately 670 mg/L. This concentration would occur only during
2.05-200 Revisedlun. 1995 PR06: Revised Nov. /998 TR80; 1/98 PR08