GENERAL45645

• Permit No: C1981044
• IBM Index Class Name: General Documents
• Doc Date: 2/28/1994
• Doc Name: PROPOSED DESISION & FINDINGS OF COMPLIANCE FOR RN2
• Permit Index Doc Type: FINDINGS
• Media Type: D
• Archive: No

conductivity over time are presented in Section 2.04.7 of the permit
application package. The only apparent trend in the plot and associated
water quality results is a reduction in the variability of sample analysis.
This may be the result of improvements in sampling procedures and analyzing
for dissolved metals.
Alluvium
Ground water levels in the alluvium have remained fairl}~ regular, with
normal seasonal fluctuations apparently related to changes in river levels.
Ground water levels in the alluvium are plotted in Figure 22 in Section
2.04.7 of the permit application package. The data indicate no impact on
alluvial water levels related to mining.
A plot of field electric conductivity versus time is presented in Figure 24
in Section 2.04.7 of the permit application package. Ocie trend apparent in
the plot is a reduction in the variability in the conductivity analyses.
This may be the result of improvements in sampling and duality assurance
procedures. All three alluvial wells showed an increase: in dissolved
solids between 1982 and 1984 and no change since that time. A correlative
increase in calcium, magnesium, sulfite, and chlorides also appeared in
Well AV-3. The source of this change is not known. However, it ie
unlikely due to mine discharge because of its location and the dissimilar
chemical composition of mine discharge.
Past and Present Inflows
A plot of the quarterly discharge for the No. 5 Mine discharge point
is presented in Permit Figure 21, in Section 2.04.7 (Hydrology
Information), of the permit application package for the period 1982
through 1992 along with the 7 North Angle discharge starting in
1989. These discharge points include inflows to both the No. 5 and
No..6 Mines, which are pumped to the surface.
The mean flow rate did not exceed the mine inflow predictions from the
previous Probable Hydrologic Consequences (PHC) evaluation. Year four of
the PHC prediction, which corresponds most closely with the 1991 mining
year, indicated combined inflows of 850 to 1,050 gallons per minute (gpm)
for the No. 5 and No. 6 Mine operations. The combined average discharge
was 673 gpm.
A mine inflow study performed for the No. 5 Mine in 1985 is presented in
Exhibit 30 of the permit application package. The results of this study
indicated that almost half of the inflow to the No. 5 Mine was coming from
a fault zone in the 2 west Main. A report on the fault zone inflows in the
2 West Area ie presented in Hxhibit 33, a Review of the Geology and
Geohydrology of the 2 West Area, Hagle No. 5 Mine.
Based upon the observed flows in the mine, it appears that a significant
portion of the inflow is coming from dewatering of the anal beds.
Additional flows are coming from fault zones and from overlying and
underlying zones. Because water level declines are being observed in the
overlying Middle Sandstone Unit, it can be assumed that some of the inflow
to the mine is from this unit. However, it ie not possible to determine
whether the Middle Sandstone water reaches the mine through existing
faults, through general seepage, or through subsidence induced fractures.
The No. 5 Mine discharge has declined slightly since 1986 despite the
advance of mining into the E seam associated with the No.. 6 Mine.
Water quality data for the fault zone inflow in the No. 5 Mine, presented
on Permit Table 73, indicates that the water is of similzir chemistry Co the
Trout Creek Sandstone. Upward flow from the Trout Creek to the E coal seam
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