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REP09004
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REP09004
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Entry Properties
Last modified
8/24/2016 11:38:45 PM
Creation date
11/27/2007 12:01:44 AM
Metadata
Fields
Template:
DRMS Permit Index
Permit No
C1982056
IBM Index Class Name
Report
Doc Date
7/12/1999
Doc Name
1998 ANNUAL HYDROLOGY REPORT REVIEW LETTER
From
DMG
To
TWENTYMILE COAL CO
Annual Report Year
1998
Permit Index Doc Type
HYDROLOGY REPORT
Media Type
D
Archive
No
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Fish Creek sandstone wells <br />Water levels in the two Fish Creek sandstone wells, 9l M001 and 91 Nt004, in the SWMD <br />continue to indicate slight drawdown due to undermining and subsidence. However, 91 bt001 <br />has recovered to levels very close to pre-subsidence levels. The Ashley domestic well in the <br />EMD is also completed in this formation and shows no impact due to mining at this time. <br />Conductivity and pH measurements of these wells indicate no change in water quality that is <br />consistent with predictions. <br />Alluvial Wells <br />Water levels continue to show seasonal variation with no apparent changes due to mining. <br />Salinity increases aze evident in alluvial wells on Foidel and Fish Creek but this increase is likely <br />not due to bedrock discharge from natural discharge points. Underground mine water discharge <br />to these two creeks are likely the cause of the observed increases in salinity over baseline levels. <br />The PHC does not address alluvial well salinity changes caused by surface water changes and <br />alluvium recharge. Well 006-AY-1 upstream of mining on Fish Creek shows increasing <br />conductivity as does welt 006-AZ-3 neaz the Fish Creek Borehole and well 008-AU-3 near the <br />Fish Creek Tipple. Lazger changes in conductivity are evident the closer the wells are located to <br />the Fish Creek Borehole, the mine portal and facility area, and spoil springs at the Fish Creek <br />Tipple. Well 008-AT-I, downstream of all mining impacts on Trout Creek indicates variation in <br />TDS from 700-900 mg/l since the inception of monitoring. The Jones domestic alluvial well on <br />Trout Creek indicates TDS of approximately 500 mg/I. Middle Creek alluvium remains <br />unaffected by underground mining activities. <br />The PHC predicts quantity impacts to the Wadge overburden and to a lesser degree the <br />Twentymile sandstone aquifer. No signiticant water quality changes are predicted. Generally, <br />data confirms these predictions at the present time. <br />Diminution of Bedrock Discharge to Alluvium and Surface Streams <br />(also Effects on Alluvial and Surface Water Oualitv As a Result of Bedrock Discharge) <br />Both of these impacts aze predicted to be small and analysis of the data does not indicate that <br />either can be detected at this time. Streamflow shows normal seasonal vaziation. <br />Subsidence Impacts on Ground Water Ouantitv <br />Review of the ground water data reveals that subsidence does appear to impact ground water <br />levels by increasing permeability due to bed separation and fracturing induced by subsidence, <br />especially in the Twentymile sandstone and the Wadge Overburden. Impacts aze discussed for <br />each ground water unit above under Dewaterine and Potentiometric Drawdown in Bedrock <br />Units. <br />Subsidence Impacts on Alluvial Ground Water in the Foidel and Middle Creek Alluvial Valleys <br />The PHC predicts no impacts to alluvial water quality in the Foidel and Middle Creek alluvial <br />valleys due to subsidence. Analysis of the data indicates water quality changes in alluvial <br />
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