2013-10-30_REVISION - M1977310 ‎(3)‎

• Permit No: M1977310
• IBM Index Class Name: REVISION
• Doc Date: 10/30/2013
• Doc Name: DRAINAGE DESIGN PLAN FOR THE JD6 MINE
• From: COTTER
• To: DRMS
• Type & Sequence: AM1
• Email Name: TC1
• Email Name: SJM
• Media Type: D
• Archive: No

JD -6 Mine — Drainage Design Plan 10
3. HYDROLOGIC CHARACTERISTICS OF SITE SOILS
The dominant soil types in the JD -6 Mine facilities area are Bodot and Ustic Torriorthents, which are
shown as soil type 23 on Figure 4 of the EPP. Additionally, a thin exposure of rock outcrop — Orthents
complex has been mapped along the ridgeline (MRCS, 2012b) in the headwaters of Sub -basin 132. The thin
soils that occur on steeper areas of pinyon - juniper woodlands in the vicinity of the JD -6 Mine (Unit 23) are
classified as fine, montmorillonitic, calcareous, mesic Ustic Torriorthents and are mapped as Hydrologic
Soil Group C (Table 4). Rocky outcrop areas are mapped as Group D. These soil groups are defined by
the NRCS (2012a) as:
Group C. Soils having a slow infiltration rate when thoroughly wet. These consist chiefly
of soils having a layer that impedes the downward movement of water or soils of
moderately fine texture or fine texture. These soils have a slow rate of water transmission.
Group D. Soils having a very slow infiltration rate (high runoffpotential) when thoroughly
wet. These consist chiefly of clays that have a high shrink -swell potential, soils that have a
high water table, soils that have a claypan or clay layer at or near the surface, and soils
that are shallow over nearly impervious material. These soils have a very slow rate of
water transmission.
Table 4. Soils Types in Vicinity of the JD -6 Mine Facilities (Sub -Basin B2)
Map
14.11 -42.23
Hydro Depth
K Sat (micro
Soil Name
Unit
Taxonomic Classification
Group (in)
m /sec)
Fine, montmorillonitic
0 -3
1.41 -4.23
Bodot, dry
(calcareous), mesic Ustic
3 -30
0.42 -1.41
Torriorthents
C 30 -34
0.00 -14.11
23
0 -4
1.41 -4.23
Ustic
Ustic Torriorthents
4 -31
1.41 -4.23
Torriorthents
31 -35
0.42 -1.41
Rock outcrop ---
88
Orthents Orthents
D 0 -60 0.00 -0.03
0 -1
14.11 -42.23
1 -14
14.11 -42.23
B
14 -24
1.40 -14.00
24 -60
1.40 -14.00
The runoff curve numbers for the site were selected based on soil type, land use, and vegetative cover. A
curve number of 73 was applied for pinyon juniper with grass understory, in fair condition (30 -70%
vegetative cover) and group C soils (Table 5). A curve number of 89 was applied to areas occupied by the
gravel access road (County Road EE19). A curve number of 85 was applied to the disturbed ground and
waste rock piles in the mine facilities area. For sub -basins containing more than one soil or cover type, a
weighted average curve number was calculated based on the relative areas of each CN. Site curve numbers
are listed in Table 6 and area - weighted average curve numbers are provided in Attachment 4.
4148A.131028 Whetstone Associates