2018-02-08_PERMIT FILE - C2010089A ‎(6)‎

• Permit No: C2010089A
• IBM Index Class Name: Permit File
• Doc Date: 2/8/2018
• Doc Name: Overburden and Topsoil Handling Plan
• Section_Exhibit Name: Section 2.05.4‎(2)‎‎(d)‎
• Media Type: D
• Archive: Yes

located in the uppermost overburden in the NHN permit area (see Section 2.04.6, Stratigraphy,
Cross Sections A -A', Map 2.04.6-4). These clay beds occur about 60 to 65 feet above the top of
the LD,, Seam and only exist in the southern part of the mineable area where the overburden
(above LDX) is at least 60 to 90 ft. thick. Map 2.04.6-3, the LDX Overburden Thickness Map,
shows the area that has sufficient overburden to contain the clay beds. These clay beds will be
mined in the area where the overburden is the thickest. When these two clay lenses are being
excavated during mining, they will be thoroughly mixed with coarser textured overburden
materials. The mixing and dilution process will be accomplished in the backfill by: 1) the
overburden shovel will be digging a full face through the clay beds, and 2) the haul trucks with
the diluted clay beds which were mixed and diluted during mining will dump their load along a
dump face which will result in significant additional mixing and diluting of the clayey materials.
After this process, the concentration of the high clay material will be minimal and compactability
of the regraded overburden will be negligible. Where the clay beds may be below the overburden
zone they will be handled as less suitable material along with the rest of the overburden and be
buried in the backfill prior to placement of Bench 1.
Bench 1 Monitoring Program
To document the suitability of the Bench 1 as potential rooting material, a Bench 1 sampling and
analysis program will be implemented. A life of mine sampling grid has been established on 500
foot centers and each sampling location on the grid corresponds to a letter/number combination.
Using this grid interval, each sampling location represents an area of about 5.7 acres in size. A
minimum of four feet of Bench 1 will be sampled prior to topsoil replacement with a hydraulic
soil sampler, a bucket auger, or other suitable equipment. Two representative samples, each
representing a two -foot depth increment will be collected. The vertical sampling increments will
be 0.0 to 2.0 feet and 2.0 to 4.0 feet. Bench 1 suitability parameters are presented on Table
2.05.4(2)(d)-1 and the results will be presented annually in the Annual Reclamation Report.
Table 2.05.4(2)(dl-1 Criteria for EvaluatinLy Bench 1 Suitabilitv
PARAMETER
SUITABLITY
H
Between 6.1 and 8.5
Neutralization Potential Ratio (NPR)
> 2
Course Fragment Content (%)
< 20
Sodium Absorption Ratio (SAR)
< 15
Electrical Conductivity (mmhos/cm)
< 6
Carbonate (%)
< 20
Selenium m)
< 1
Texture
All soil textures except: s, Is, sc, sic, c
'This value for selenium was chosen based on guidance from Dave Dearstyne of NRCS and recent data that other states are
using. Mr. Dearstyne is currently working extensively (2008) with the Selenium Task Force on the western slope and is very
knowledgeable about this issue. Mr. Dearstyne noted that there is no concern for selenium unless Mancos shale strata are being
placed near the surface. At the NHN Mine, no Mancos shale has been encountered in the overburden. Also, all tests of water
soluble selenium in the pre -mine soil survey of NHN Mine show all values less than 0.1 ppm. Mr. Dearstyne believes a threshold
suitability level of 0.2 ppm in the topsoil material and 1.0 ppm in the subsoil material is adequate. These are the levels proposed.
Section 2.05.4(2)(d) Page 2 January 2018 (PR -02)