2008-02-29_REPORT - C1982056

• Permit No: C1982056
• IBM Index Class Name: REPORT
• Doc Date: 2/29/2008
• Doc Name: 2007 Annual Hydrology Report
• From: Twentymile Coal Company
• To: DRMS
• Annual Report Year: 2007
• Permit Index Doc Type: Hydrology Report
• Media Type: D
• Archive: No

• No unusual observations are noted with respect to Foidel Creek alluvium groundwater levels. The historical
increasing conductivity trend in we11001-S-5 (Figure 32) stabilized in 2004, and appears to be increasing again
through the end of 2007.
No unusual observations are noted with respect to Fish Creek alluvium groundwater levels. The general water
level decline noted in well 006-AY-1 (Figure 34) since 1995, appears to continue in 2007. Overall, fluctuations
at this well are insignificant. No other notable water level observations are apparent based upon review of the
2007 data. Field conductivity readings at this well appear stable over the last few years. Two new alluvial wells
(AVF-13 and AVF-14) were installed in August 2001, and one (AVF-15) in June 2002. The only unusual
observation made to date were elevated iron concentrations in 2003 and 2004, some of which may be related to
subsidence ponding. These levels appear to have returned to those seen with normal seasonal fuctuations. The
data base for these sites will require expanding before a complete assessment can be made.
Surface Water: Recorded surface water flows for Foidel Creek, Fish Creek, and Trout Creek were generally
low in comparison to TCC's historic record. A stream gage study was initiated by TCC with the aid of a
consultant in the summer and fall of 2007. This study will continue in the spring, summer and fall of 2008. A
discussion of this study, including results for re-evaluating stream rating curves will be included in the 2008
AHR.
Conductivity concentrations at site 301, 69, and 1005 on Trout Creek appeared elevated during the spring runoff
• season in April. This may be the result of upgradient spring runoff flushing through the old P & M mine area.
No other notable water quality impacts are evident at any surface water sites monitored during 2007.
Spoil SprinQS: Recorded 2007 spoil spring discharges remain negligible and, therefore, did not constitute a
significant portion of discharge from the TCC mine area with the potential to impact off-site areas. Discharges
from sedimentation ponds predominately occurred in conformance with applicable CDPS permit limitations and
therefore did not constitute significant impacts to receiving waters. Mine water discharge site 109 did not
discharge to Foidel in 2007. Site 115 did not discharge to Fish Creek in 2007. TCC redirected mine water from
the site 115 source in 2005 to underground locations for dust control.
Mine Discharge: No significant hydrology impacts, attributable to CDPS discharge activities at the Foidel
Creek Mine, were noted during 2007.
Mine Inflow: No unusual occurrences of inflow were noted as a result of the Annual Mine Inflow study.
Inflows are within the projected flows presented in the permit. Water quality has not changed significantly and
appears to Horror the quality of the adjacent spoil water. It appears that the elevated EC and iron readings are
associated with the water that has pooled in the mine sump, which is in contact with the overlying Marine Shale.
This contact has provided the opportunity for additional salts and iron to be leached from this unit. The pumping
of the sump should see a decrease in the elevation of the pool over time, with an anticipated decrease in the EC
and concentration of iron in the effluent.
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