2009-11-13_PERMIT FILE - C1982056 ‎(3)‎

• Permit No: C1982056
• IBM Index Class Name: Permit File
• Doc Date: 11/13/2009
• Section_Exhibit Name: Exhibit 26C Coal Refuse Disposal Area Expansion
• Media Type: D
• Archive: No

• Subsurface Conditions
The subsurface conditions encountered in the test holes and test pits were fairly consistent and generally
consisted of fill materials used to reclaim the previous surface mining operation at the site. The reclaim fill
materials consisted of a layer of topsoil and organic fill materials overlying reclaim spoils to the maximum
depth investigated, 40 feet. The logs of the exploratory test holes are shown in Figure #3. The logs of the
exploratory test pits are shown in Figure #4. The associated Legend and Notes for the test holes and test
pits are presented in Figure #5.
The topsoil and organic fill materials were encountered in all of the test holes and pits and generally ranged
from 12 to 18 inches in thickness. Reclaim spoils were encountered beneath the topsoil and organic
materials in all of the test holes and test pits and extended to the maximum depths investigated in each test
hole /pit. The reclaim spoils generally consisted of sands, clays and silts with bedrock fragments, which
were low to highly plastic, medium dense to dense, dry to moist and brown to gray in color. The bedrock
(sandstone and claystone) fragments generally ranged in size from gravels to large boulders. Samples of the
reclaim spoils classified as SC -SM to CL -CH soils in accordance with the Unified Soil Classification
System.
Groundwater seepage was only encountered in one test hole at the time of drilling. Groundwater seepage
was encountered in test hole 5 at a depth of 8 %2 feet beneath the existing ground surface at the time of
drilling. The seepage is likely due to the proximity of the test hole to an existing drainage ditch, which was
• flowing at the time of our field investigation. It should be noted that groundwater conditions can be
expected to fluctuate with changes in precipitation and runoff at the site.
Coal Refuse Disposal Area Analysis & Design
The location of the proposed CRDA Expansion was chosen by Twentymile Coal based on previous
investigations and design for the CRDA. Analysis and design related to any potential acid or toxic
properties of the coal refuse is not within the scope of this investigation.
Volume and Configuration
The required volume of the proposed CDRA Expansion requested by Twentymile Coal Company was
approximately 20 million cubic yards (mcy). The design configuration presented in this report contains
approximately 20.7 mcy. The maximum height of the CDRA will be on the order of 200 to 250 feet above
the existing ground surface. The top of the CDRA will slope down to the southeast to minimize runoff over
the face of the fill slope. The Final Grading Plan for the CRDA is presented in Figure C -101. The Phase I
Grading Plan is presented in Figure C -102.
The refuse pile includes a sloped face at a 3(H) to 1 (V) slope configuration with 20 foot wide benches and
associated ditches at 50 feet vertical intervals. This provides an overall slope configuration of
approximately 3.5 to 1. Typical Sections through the proposed CRDA are presented in Figure C -301. The
• benches will be constructed to slope away from the face of the slope to a ditch, which will flow around the
Job Number: 08 -7915 NWCC, Inc. Page 5
Revised 10/12/09