2010-04-20_REVISION - M1977300 ‎(9)‎

• Permit No: M1977300
• IBM Index Class Name: REVISION
• Doc Date: 4/20/2010
• Doc Name: 12-20
• From: Whetstone
• To: DRMS
• Type & Sequence: TR11
• Media Type: D
• Archive: No

Environmental Protection Plan, Schwartzwalder Mine 14-3
• on these theses results, material in the East and West Waste Rock Piles, and the fill adjacent to Ralston
Creek have low potential to generate acidic drainage.
Table 143. Summary of Acid-Base Accounting Results

Sample Location

(ft)
J
Depth Years

Exposed to
ANP

t CaC03/kt
AGP

t CaC03/kt
NNP

t CaCO3/kt
ANP/AGP
Weathering
XT 11. [17....4.. DLn11 Daa
South End, Central Bench
South End, Central Bench
South End, Central Bench
North End, Central Bench
North End, Central Bench
North End, Central Bench 1.5
6
11
1.7
6
11.5 <1*
10-17
10-17
<1*
10-17
10-17 214
175
179
188
123
160 8
23
14
8
38
22 206
152
165
180
86
138 28.5
7.5
12.7
22.7
3.3
7.4
Q.,..t6 Woe*- Rnek Pila
North End, Top V V
North End, Top
North End, Top
South End, Top
South End, Toe 1.5
6
10.5
1
2.5 15-17
15-17
15-17
13-18
13-15 186
162
174
229
157 29
38
33
28
68 158
124
141
201
89 6.5
4.3
5.3
8.2
2.3

Average 177 28 149 10
* = moved in six months prior to ABA testing
• (iii)Acid Consumption Tests
An evaluation of the potential for acid-leach reprocessing of the waste rock piles was performed in 1986 by
Colorado School of Mines Research Institute (Chlumsky, 1986). Results of the study indicated that the
acid consumption per ton of waste rock was between 400 and 420 pounds of sulfuric acid. This
neutralizing potential is equivalent to about 160 t CaC03/kt assuming 40% solution of sulfuric acid, and is
in good agreement with the results of ABA testing.
(iv) Impact Analysis
Waste rock from the mine was placed in two external dumps that are located adjacent to Ralston Creek
upstream of the mine (Figure 2-1). The stability of the waste rock piles was investigated by McDermid
(1983a, 1983b) and hydraulic control structures were constructed to protect the piles from the 100-year
flood event (Shepherd Miller, 1999). The control structures include an energy dissipater located in the
ephemeral drainage near the east waste rock pile and rip rap on the side slopes. Additionally, the waste
rock piles were recontoured to a stable 2H: IV slope configuration.
R.G. Otto & Associates (1984) performed a detailed survey of surface and groundwater quality to assess
the impact of runoff and seepage from the waste rock piles on the water quality in Ralston Creek. Surface
water samples were collected upstream and downstream of the waste rock piles and groundwater samples
were collected down-slope of the disposal site from September 1983 through August 1984. The study
concluded that the waste rock piles had no measurable impact on water quality in the stream, with the
possible exception of stream uranium levels. The uranium data were inconclusive for determining impact,
and the uranium levels in Ralston Creek downstream of the waste rock piles were below the Colorado
Basic Stream Standards.
Subsequent water quality monitoring on Ralston Creek from 1984 to 2009 has not indicated impacts to
• water quality in the creek. Laboratory data and the E.C. survey conduct d in November 2008 (Section
8(e)(ii)) showed no impact from the waste rock piles on Ralston Creek (Figure 8-22).
4109C.100419 Whetstone Associates