2010-07-27_PERMIT FILE - M2009076 ‎(12)‎

• Permit No: M2009076
• IBM Index Class Name: PERMIT FILE
• Doc Date: 7/27/2010
• Doc Name: Adequacy Response, Ex. C- Mining Plan
• From: Venture Resources
• To: DRMS
• Email Name: ACS
• Media Type: D
• Archive: No

• consolidation is not occurring at an acceptable rate, mechanical compaction may be required in the future. In either
event, Venture Resources will seek permit modification with the DBMS.
TRI/Environmental (TRI) and Advanced Terra Testing (ATT) each examined a representative dry mill tailings
sample. This is the same material that was yielded from the waste stream characterization testing described earlier
and explained in the appendix, Waste Stream Characterization. TRI's work will focus on the interface relationships
between the tailings and the liner system. ATT's work will focus on the strength properties of the tailings. These
independent reports and analysis can be found in the appendix of this Exhibit C.
TRI rePorts the "as-received" dry tailings sample moisture content was 5.09% with a dry density of 93.3 lb/ft3 (1.26
ton/yd) and a total density of 98.0 lb/ft3. (1.32 ton/yd3) - determined by ASTM D-2216.
TRI's first test was a Particle Size Analysis, determined by ASTM D-422. In summary, 34.6% was retained by a
No. 100 sieve. For purposes of this project, it has been determined that this portion shall be defined as the Coarse
Fraction. It follows that 65.4% ap ssed a No. 100 sieve. This portion shall be defined as the Slimes Fraction. These
determinations should not be confused with the traditional differentiation of sand and fines with a No. 200 sieve
split. The embankment will require a coarser fraction for a higher degree of stability.
Next, TRI performed a series of Proctor Compaction Tests, determined by ASTM D-698 - Method A. The dry
tailings (as a mixture of coarse + slimes) showed a maximum dry density of 111.2 lb/ft3 (1.5 ton/yd3) with an
optimal moisture content of 14.8%. For the Coarse Fraction a maximum dry density of 104.3 lb/ft3 (1.4 ton/yd3) was
reported with an optimum moisture content of 11.4%. The Slimes Fraction was similar, reporting a maximum dry
density of 109.1 lb/ft3 (1.47 ton/yd3) with an optimum moisture content of 16.1%.
ATT performed a series of Consolidation Tests to also look at density characteristics during consolidation. ATT
utilized ASTM D-2435 standards for this. The Coarse Fraction and Slimes Fraction were prepared to a 30% pulp
density to mimic the target tailings discharge from the mill down the tailings pipeline. The results of this are as
• follows:
Coarse Fraction Consolidation
Before Test After Test
Wet Density 113.91b/ft3 (1.5 ton/yd3) 118.5 lb/ft3 (1.6 ton/yd3)
Moisture Content 25.3% 25.5%
Dry Density 90.9 lb/ft3 (1.2 ton/yd) 94.5 lb/ft3 (1.3 ton/yd)
Slimes Fraction Consolidation
Before Test After Test
Wet Density 110.7 lb/ft' 1.5 ton/yd3) 121.41b/ft3 (1.6 ton/yd3)
Moisture Content 43.3% 30.4%
Dry Density 77.21b/ft3 (1.0 ton/yd3) 93.1 lb/ft3 (1.3 ton/yd)
These values provide for a standard of comparison for evaluating consolidation during operations, utilizing a core
sampling procedure that has been already been described earlier in this Exhibit.
Several assumptions have been made to define representative confining pressures, necessary for this battery of
testing. The greatest height of the proposed tailings impoundment is achieved at Bench 5 and is approximately 88 ft.
(reference Exhibit E cross-section drawing El 1). Based on this height, and the Proctor compaction density results of
the dry tailings of 111.2 lb/ft3, a confining pressure of - 10,000 lb/ft (69.4 lb/in2) can be assumed. For the interface
friction and triaxial shear testing, the maximum confining pressure was increased to 15,000 lb/ft2 (104 lb/in2) to
allow for a factor of safety ;z 1.5 It shall be pointed out that this maximum depth is only concentrated in the
centerline of the impoundment because of the placement in the intersecting planes of the dry gulch.
Hydraulic conductivity of the tailings sample was examined by TRI (ASTM D-5084 Method Q. Utilizing samples
described previously as Coarse and Slimes Fraction the average hydraulic conductivity was reported as:
• Coarse Fraction kCOa, e = 68 x 10-6 cm/sec
Slimes Fraction k,1i„,,, = 3.5 x 10-6 cm/sec
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