2008-05-21_REPORT - C1981028

• Permit No: C1981028
• IBM Index Class Name: REPORT
• Doc Date: 5/21/2008
• Doc Name: 2006 & 2007 AHR Review Memo
• From: DRMS
• To: File
• Annual Report Year: 2006
• Permit Index Doc Type: Hydrology Report
• Email Name: TAK
• Media Type: D
• Archive: No

Require-

Requirement Require-ment
citation ment
complied
Comment
with ?
es / no
DRMS previously concluded the Keenesburg Mine does not
have the potential to negatively impact ground water and,
therefore, a ground water point of compliance is not
warranted (Memo to 2004 AHR file, dated 7/6/05). The
memo of 7/6/05 also explains that if coal spoil or ash
leachate migrated from the pit through eolian sand, Ennis
alluvium, or the Laramie sandstone and coal, attenuation and
dispersion would result in levels of TDS and SAR in ground
water that are near pre-mining conditions within a few
hundred feet of Keenesburg's pit. The mine monitors water
quality in the Ennis alluvium and eolian sand in well DH-96,
R. Basic Standards CWQCC located approximately 6,000 ft. downgradient from the
for Ground regulations yes mine's pits. Multiplying conductivity by 73.6% to derive
Water 41.4 and 41.5 TDS, the concentration of TDS in well DH-96 averaged
approximately 1271 mg/l in 2006 and 1242 mg/1 in 2007.
(The 73.6% conversion factor is based on the observed
relationship between field conductivity and lab samples from
the DH-96 well.) The 2006 and 2007 TDS values are well
below a 1750 mg/l background level identified in the 7/6/05
memo.
Each pit disrupts the potentiometric surface. After final
S. Restoration of backfilling, the pits can be expected to show full recovery
ground water CDRMS of the potentiometric surface outside of the pits and water
recharge to regulation yes table (unconfined) conditions inside the pits. No
approximate 4.05.11(3) significant formation of surface spoil springs is expected
premining rate due to the flat topography; therefore, there will be no loss
of ground water flows to surface waters.
The Probable Hydrologic Consequences section of the
permit application predicts no appreciable impacts to
T. Prevention of ground water systems outside the permit area. Water
adverse impacts CDRMS quality data from well DH-96 indicate there have been no
to ground water regulation yes adverse impacts to ground water in the Ennis alluvium and
systems outside 4.05.11 eolian sand outside the permit area, approximately 6,000 ft.
the permit area downgradient from the mine's pits.
U. Prevention of The approved post-mining land use of most of the permit
impacts to area is rangeland (a few acres are approved for
ground water CDRMS commercial/industrial gas well use). As previously
that adversely regulations discussed, ground water in the Ennis alluvium and eolian
impact the 4.05.1(2) and yes sand have not been adversely impacted by mining and
postmining land 4.05.11 reclamation operations at the Keenesburg Mine. Ground
use within the water in the Laramie coal and sandstone is not likely to have
permit area had adverse impacts as explained in the previous discussion
of Basic Standards for Ground Water.
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