PERMFILE56743

• Permit No: C1982057
• IBM Index Class Name: Permit File
• Doc Date: 12/11/2001
• Doc Name: Comparison of Predicted Impacts to Water Quality Data Thru August 1995
• Section_Exhibit Name: TAB 17 APPENDIX 17-2
• Media Type: D
• Archive: No

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• APPENDIX 17-2
Comparison of Predicted Impacts to Water Quality
Oa [a Through August, 1995
Surface Watc•r. The key downstream surface water monitor used for impact assessment Ss
Site SG5 IDry Creek). No impacts on Sage Creek have been observed since: 1) no spoil
water viii discha rg e~ into that basin and 2) tt,e only NPDES Impoundment Sn that bast n, 009,
has yet to discharge: (as of October, 1995).
Table 17-29 ITab 171, Item 5 (p. 79), predicts a 2 percent increase at Slte SG5 Sn June
through September average TDS values (from 1048 to 1071 mg/11 due to mine pit pumpage of
Wadge coal Bind overburden water. Item 7 (p, 80) predicts a 119 percent increase in June
through September average TDS values (from 1048 to 2245 mg/1) due to spoil eater. Table
17-2-1 prov:.d es average June through September TDS values for every year since August,
1990 (when ni ni ng commenced). These values ranged from 890 mg/1 in 1993 to 1443 mg/1 Sn
1989 with a maximum observed TDS of 1562 mg/1 (September, 1989). Figure 17-2-1 plots TDS
values observed at SG5 since 1983. Predictions were based on 4500 mq/1 of TDS discharging
from the spoils into sediment ponds. Figure 17-2-2 (005) and 17-2-3 (006) plots TDS
values for each sediment pond since discharges began. Revlev of these two figures
rndtca[e Chat TDS vial ues have yet not come close to that predicted maximum TDS value.
Ground Water. Table 17-29, Item 6 (Tab L7, pgs. 79-80) makes predictions for TDS
increases for the Y7.adge coal seam, Wadge overburden, and the alluvium. Each eater-bearing
• zone is drsru ss ed separately below.
A five to seven percent increase of TDS va"sues was predicted in the Wadge overburden.
Figure 17-2-4 plots TDS values for the key yell monitor of the overburden Sn the north
pit, Gw-S2W-14OV. Prior to mining in the north area (November, 1992), Well 14OV had an
average 7DS of 342c.~ mg/1 Ira nge 2856 to 3758 mg/1). Only the most recent sample (June,
19951 had a TDS value (4200 mg/1) greater than the premining average. More data will be
needed to sae if that was an anomalous value or if the increasing TDS trend continues.
In the south prt area (referred [o in the Tab 17 text as the center pitl, the key well
mor.r :or cf the overburden is GW-52W-17 OV. Figure 17-2-5 plots TDS values for this well.
The pre mr ninq 1196E to 19901 TDS average for this well was 7855 mg/1 Ira nge 6858 to 8586
nag/il. F.eview e[ Figure 17-2-5 indicates that TDS values after 1990 still fall within the
p:emrniny range.
A ":4 to 38 percent Increase of TDS values was predicted for the Wadge coal seam. Figure
17-2-6 p:•.ots TDS values for Well GW-52W-14 W, [he key Wadge coal monitor in the north pit
area. Prior to 1993, little or no eater existed Sn this well; therefore, premi ning
condrticns could net be determined. More data will be needed to determine this well's TDS
crcna.
'We:l GW-;~4:-1'iW as the hey Wadge coal moni ter in [he south pi[ area. Figure 17-2-]'plots
T D.3 cal u~zs fur this we11. The premr ni ng 119138 [0 1990) TDS average for [his well vas 821
• i~~,!1 1552 [c. 1ti62 mg/1 range). Review of Figure 17-2-7 indicates that only [he most
resent fi~fa y, 1995) TDS value 11710 mg/1) exceeds the pr=mining range. More data will be
needed to see if that vas an anomalous value or if the increasing TDS trend continues.
17-2-1