REP30848

• Permit No: C1981044
• IBM Index Class Name: Report
• Doc Date: 12/11/2001
• Doc Name: 2000 AHR Text
• Permit Index Doc Type: hydrology Report 2000
• Media Type: D
• Archive: No

RAG. Empire Corporation 2000 AHR
• GROUNDWATER MONITORING
BEDROCK
Three sandstone aquifers are monitored at the site. They are, in ascending order: Trout Creek
Sandstone (1 well), Middle Sandstone (6 wells), and Twenh~mile Sandstone (3 wells). The #5
and #6 Mines are between the Trout Creek Sandstone and the Middle Sandstone.
WATER LEVELS
The potentiometric surface represented by water Level measurements in the Trout Creek
Sandstone 5 Mine well (Fig. 3), has recovered to the levels measured in 1986 through 1988.
This recovery is apparently from a reduction in pumping for use by the mining operation. The
well is used for water supply as well as monitoring. Historical water level fluctuations of 20 to
200 feet have been observed at this well but no seasonal pattem is evident. The Okie Plaza
Trout Creek well was abandoned in June 1994 as mining advanced through its location. See the
1994 Annual Hydrology Report for data on this well.
The water levels in the Middle Sandstone formation as measured in wells TR-4, TR-7a, 81-O1,
• 83-O1, 83-02, and 83-03 show fluctuations which are apparently related to dewatering and
subsidence associated with Mines 5 and 6. Wells TR-4, TR-7A, and 81-O1 displayed unusually
large fluctuations during 2000. RAGEC will continue to monitor this trend toward large
fluctuations in water level. The water levels in Well 83-02 (Figwe 8) show a different pattem.
The water level decline of about 150 feet from 1987 to mid 1989 in Well 83-02 is determined to
be related to mine dewatering as Mine 5 workings approached the location of the well. The
more abrupt 200 foot decline in water levels observed near the end of 1989 and beginning of
1990 is thought to be a drawdown response due to subsidence as it is located on only a few
hundred feet horizontally from an F seam longwall panel which was mined in a similar time
frame. The water level stabilized until 1994 when it recovered to the 1983 levels. Wells TR-4
and 83-03 are located at greater distance horizontally from the active operations for mines 5 and
6. Water levels in Well TR-4 (Figure 4) historically appear to be related to the fluctuations
observed on all three of the down gradient Middle Sandstone Wells: 81-01, 83-01 and 83-02.
The water level decline in TR-4 prior to 1984 and the subsequent recovery up to 1988 closely
parallels the trends observed in Wells 8]-O1 and 83-01. The decline during the first part of 1991
also parallels the Vend in these two wells. However, the rapid decline during the last part of
1989 and the first part of 1990 appears to follow the trend observed in Well 83-02 although the
magnitude of decline is considerably less. Well 83-03 (Figure 9) is the Middle Sandstone
monitoring well located furthest (more than 1.5 miles) from active underground operations for
Mines 5 and 6. The overall trend from 1984 through 2000 suggests a similar trend to the other
Middle Sandstone wells. The long term decline could be a presswe response due to the overall
drop in potentiometric levels in the Middle Sandstone in the vicinity of Mines 5 and 6. Except
for Well 83-03, the water levels in the Middle Sandstone wells had either recovered or
stabilized in 1995. The water level data collected for the other Middle Sandstone wells
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