2021-04-14_PERMIT FILE - C1996084 ‎(8)‎

• Permit No: C1996084
• IBM Index Class Name: Permit File
• Doc Date: 4/14/2021
• Doc Name: page 2.05-46 to 2.05-123
• Section_Exhibit Name: Section 2.05 Operation and Reclamation Plans Part 2
• Media Type: D
• Archive: No

Rule 2: Permits
A comparison of the field and laboratory parameters for PRGTY -1 and PRGTY -2 show
• minor (less than 10 %) changes from Pre - mining to Post Mining for pH, Conductance,
Sulfate, Calcium, Magnesium, and Potassium. A major increase (greater than 50 %) was
observed for Sodium, Chloride and Sodium Absorption Ratio (SAR). The percent
change was almost identical in comparing the deviation Pre to Post - Mining both
upstream and down stream from mining. This demonstrates that there has been a
significant change in water quality from 1996 -2000 compared to 2002 -2009, especially in
regard to Sodium and Chloride. Similar observations can be made for LC -1 and LC -2
except that major increases (greater than 50 %) were also observed for Conductance and
Iron. Here again, the percent change was almost identical in comparing the deviation
from Pre to Post - Mining water quality both upstream and down stream of mining activity.
The observed similar water quality changes upstream and downstream of mining would
indicate that another source (likely coal bed methane dewatering) is causing the changes
in the local water quality and mining appears to have had little or no effect to the
hydrologic regime.
Surface water run -off from the site is contained and treated by sediment ponds. These
ponds discharge infrequently, commonly going several years with no discharge.
Additionally, mining did not intercept any alluvial aquifers that may have contributed to
pre - mining surface water quality. Deep aquifers were sampled from 1996 -1999 as part of
the baseline monitoring for the proposed LCM Underground mine. These aquifers
tended to be alkaline with higher levels of sodium and chloride than the surface waters in
the area. It is not known if the CBM Wells are producing water from these or similar
zones. Five years of monitoring surface water quality post- mining demonstrates that the
• Lorencito Canyon Mine has not impacted surface waters and surface water monitoring
will be terminated as of 2009.
Springs and Seeps and Stock Ponds
Monitoring of these sites was terminated in 2007 by Technical Revision -15.
Alluvial Groundwater
A comparison of the field and laboratory parameters for MWLC -1 and MWLC -2 show
minor (less than 10 %) change from Pre- mining to Post Mining for Depth, pH, Sulfate,
Calcium, Magnesium, and Hardness. A major increase (greater than 150 %) was observed
for Sodium, Chloride and Sodium Absorption Ratio (SAR). The percent change was
almost identical in comparing the deviation from Pre to Post-Mining both upstream and
down stream of mining. This demonstrates that there has been a significant change in
water quality from 1996 -2000 compared to 2002 -2009, especially in regard to Sodium
and Chloride. These changes are similar to the changes for LC -1 and LC -2 and provide
evidence that surface water is communicating with and influencing the alluvial
groundwater quality. Here again, the percent change was almost identical in comparing
the deviation from Pre to Post - Mining both upstream and down stream of mining activity.
Five years of monitoring groundwater quality post - mining demonstrates that the
• Lorencito Canyon Mine has not impacted alluvial aquifers and groundwater water
monitoring will be terminated as of 2009.
TR -16 Page 2.05 -108 (Revised 01 /11 /10)