2013-01-29_PERMIT FILE - C1981022A ‎(3)‎

• Permit No: C1981022A
• IBM Index Class Name: Permit File
• Doc Date: 1/29/2013
• Section_Exhibit Name: 2.05 Operation and Reclamation Plans
• Media Type: D
• Archive: Yes

Strricvr - 2.05.6
In general, depression of the water table near the mine is expected to be both minor and 1«alized due
• to the re]atively low permeabihty of the ass«iated stntigraphic units. Additionally, ground water
flow patterns in the overlying perched aquifer system may also be affected by downward leakage
through subsidence fractures. This may result in partial or full drainage of the perched aquifers and
may affect the discharge of springs and seeps. Impacts on perched aquifers and azs«iated springs
and seeps due to secondary subsidence effects are not expected to be significant since the perched
aquifers are very limited in areal extent, potential subsidence areas represent a relative small pottion of
the total permit area, and there are no known adjudicated or other beneficial rues from the perched
aquifer system
Upon completion of operations and final mine reclamation and closure, ponions of the underground
workings will gradually fill with water resulting in reestablishment of the water table at approximately
the same level which existed prior to mining. Any minor changes in water levek which may «cur are
not expected to be significant since the overall hydrologic balance within the ground water bazin will
not be effected. Reductions in the quantity and availability of ground water az a result of alterations
to the ground water flow patterns are expected to represent a minor percentage of total ground water
flows within the bazin, will be limited in areal extent, and should be temporary in nature. In addition,
reductions in groundwater flows are not expected to adversely impact ground water users since
beneficial ground water rue in the general area u limited to the North Fork alluvium/colluvium which
is stratigraphically below and effectively hydraulically isolated from the sequence to be affected by
mining by low pem~eabiliry bedr«k. Potential impacts to springs and seeps discharging from the
perched aquifer system are discussed below.
OMI's mining activities may result in some drainage and dewaering of overlying perched ground
water aquifers az a result of vertical seepage through subsidence fractrtres. Consequently, springs and
seeps discharging from the stratigraphic units containing the perched ground water maybe effected.
• OMI will attempt to m,~,mnr subsidence to the extent possible while m~~rimning recovery of
available coal resources. Subsidence will be controlled through the use of longwall mining methods,
maintenance of bamer pillars, limiting extraction in critical areas, and proper mining and roof control
design and operations practices. Effective control of subsidence will limit fracturing of overlying
strata and the consequent potential for drainage through subsidence fractures. Additional discussion
of potential subsidence effects is presented in Section 2.05.6, Subsidence Survey, Subsidence Control,
and Subsidence Monitoring Plan
Although subsidence fracturing may result in limited discharge from ass«iated perched ground water
aquifers, changes in the general potentiometric surface are not anticipated since the perched aquifer
system u isolated from the water table aquifer by the low pemreabiliry interbedded silutones and
shales of the underlying formations, storage volumes in the isolated perched aquifer «currences are
minor compared to the regional system, and any subsidence fractures are expected to gradually fill-in
with natural consolidation and mineral deposition. L«alized changes in the potentiometric surface
for the perched aquifers within mine subsidence areaz may have some effect on ground water levels
and flow rates in those ground water aquifers which supply surface springs and seeps.
A total of eleven springs were I«ated and monitored by Western Slope Carbon from 1983 through
1987. Seven of the springs (Nos. 1 - ~ are ephemeral and four (Nos. 8 - 11) are peremiaL The
perennial springs have an average combined total recorded flow of only 23 gpm or 0.05 cfs and az
such do not represent a significant ground water resource. If, however, discharge from any seeps or
springs which are beneficially utilized is documented az having decreased below bazeline conditions az
- a result of mining-related activities, OMI will mitigate these impacts through augmentation of any
affected water rights, monetarycompettsa[ion, development of alternative watering facilities such az
guzzlers, or other appropriate mitigation meazures.
• As ground water encounters freshly exposed subsurface materials in the mine, oxidation and
weathering will cause changes in ground water chemistry including increases in TDS and the
concentrations of individual chemical constituents. Over time these increases will stabilize and start
PR04 2.05-95 Revised August 2000