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2012-12-06_REVISION - C1981008 (4)
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2012-12-06_REVISION - C1981008 (4)
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Last modified
8/24/2016 5:11:12 PM
Creation date
12/10/2012 8:34:51 AM
Metadata
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Template:
DRMS Permit Index
Permit No
C1981008
IBM Index Class Name
REVISION
Doc Date
12/6/2012
Doc Name
Bond Release Request (Part 1 of 2)
From
Western Fuels Colorado
To
DRMS
Type & Sequence
SL14
Email Name
MLT
SB1
Media Type
D
Archive
No
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The pertinent water wells to consider for the discussion of flow and recharge are the <br />upstream wells: GW N38 (in overburden) and GW N37 (in coal) and the downstream <br />wells GW -N18 (in overburden) and GW -N17 (in coal). The cross section at the top of <br />Map R -2 shows the area between the two sets of wells. As is seen from this cross section, <br />wells GW N38 and N37 are very shallow (less than 13 feet to the surface). Since these <br />wells are so shallow and the recharge areas are very small, and there is very little <br />irrigation upstream, the only water that reaches these wells are occasional precipitation <br />recharge and some seepage from the CC Ditch. It is expected that these wells would be <br />dry on many occasions. The pre -mine well data bears this out, since the well GW N38 has <br />been mostly dry, as shown in Figure 1 attached to this bond release. When water is <br />present, it is minimal in flow and the data shows a fairly constant elevation of <br />approximately 5740 feet to 5750 feet. Seepage from the CC Ditch most likely accounts for <br />the fluctuations in elevation in the post mine period. <br />Figure 2 shows the same well but instead of a pH comparison in Figure 1, a TDS <br />comparison is used in Figure 2. This is discussed later in the groundwater quality <br />discussion. <br />The downstream overburden well, GW -N18, is the best indicator of what the effects that <br />the mining has had on the groundwater in and around the permit area. As shown on <br />Figure 3, the pre -mine levels fluctuated between 5640 feet during dry periods of the year <br />and 5666 feet during periods that were affected by irrigation. In the pre -mine condition, <br />most of the area north of the well was irrigated and this recharge moved downward in the <br />overburden and found its most permeable zones to move southwest along the strata dip. <br />After mining, the overburden water elevation has been more or less constant at <br />approximately 5640 feet elevation. During the period when the mining was near the well, <br />sampling was temporarily suspended. <br />Since the well level has been relatively constant after mining, this shows that the pre -mine <br />fluctuations from irrigation are not yet present in the well. This means that the recharge <br />water from irrigation is making its way down the spoil and is not yet influencing the well <br />to a large degree. However, we know that some spoil water is getting to the well since <br />there is a consistent (but slight) drop in pH and consistent (but slight) increase in TDS <br />versus the pre -mine condition. <br />The location of the current mining area and the pit pump are shown on Map R -2. Pit <br />pumping prevents the ground water level from rising above the pump during operations. <br />Once mining is finished and no more pit pumping occurs, the spoil should fill up <br />completely and it is possible that the water level in Well GW -N18 will increase. Future <br />monitoring will determine these changes. As the data shows in Figures 3 and 4, this has <br />not yet occurred. At a later date, as predicted in the PHC of the permit, the spoil water <br />may begin to surface as a spoil spring at the low point of the spoil area. As of August <br />2012, no springs have developed anywhere in the mine backfilled area. <br />SL -14 03DEC12.wpd 56 <br />
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