PERMFILE59255

• Permit No: C1980007
• IBM Index Class Name: Revision
• Doc Date: 12/2/2004
• Doc Name: 2.05.6‎(3)‎‎(a-c)‎ Protection of Hydrological Balance Part 3
• Type & Sequence: PR10
• Media Type: D
• Archive: No

West Elk Mrne
material to be on the order of 1.2 x 10~ cm/sec. This permeability contrast will cause most of the
leachate water to perch within the refuse and above the native soils. A shallow water mound will
build within the pile and cause the water to migrate Iateratly to sma[1 seepage azeas at the edge of
the pile. Here, it will enter the surface water collection system and be routed to a sedimentation
pond.
An analysis was performed for the RPE to determine leachate production, and is presented in
Exhibit 70. Rockdrains constructed under the base of the RPE will capture water that may
migrate down through the pile. The outlet of the drains discharge into the RPE pond, and will be
discharged along with surface water runoff that has accumulated in the pond, in compliance with
MCC's NPDES permit. In addition, Phases 1 and 2 of the RPE have been lined with a HDPE
liner. The soils investigation of the RPE azea indicated that the majority of this area is gravel,
with high permeabilities. Beyond the Phase 2 boundary, the subsoil is a clay-rich colluvium with
low permeability. As MCC has included rock drains and a HDPE liner (for Phase 1 and 2) into
the construction of the RPE, and will build future phases in an area that has clay subsoil with low
permeability, it is very unlikely that there will be a negative impact on the quality and quantity of
groundwater in the vicinity of the RPE.
\J

Table 64
Avers a Acid-Base Potential for Overburden Sam les

Location of Samples Sulfur Form Used for
Calculating
Acid-Base Potential Weighted-Average
Acid-Base Potential
(t CaCO3 eq./1000 t material)
F Seam Roof ritic +8.3
F Seam Floor ritic -2.2
F Seam Total ritic +1.9
E Seam Roof total +75.7
E Seam Floor total +t6.5
E Seam Total total +54.4
B Seam Roof total +84.3
B Seam Floor total +12.3
B Seam Total total +66.0
g + E Total total +61.2
g + F Total +~ 9.5
Total of A(I Strata +25.3
Monitoring, Protection, and Mitigation of Probable Hydrologic Consequences - 2.05.6
(3)(a&b)
Surface Water
Despite the fact that MCC's fmdings indicate that there will not be significant hydrologic
consequences to downstream water users, wetlands, other aquatic resources, etc., MCC currently
has in place and will expand, as necessary, its comprehensive monitoring and mitigation program.
For example, the Colorado Water Court decree for the Dry Fork Augmentation Plan (included as
Exhibit 52) provides a detailed description of those stream gages that will be utilized to determine
whether hydrologic changes are occurring in the Dry Fork basin as a consequence of subsidence.
1.05-153 RevisedNwember 1004 PRl0