2008-12-19_REVISION - M1980244 ‎(5)‎

• Permit No: M1980244
• IBM Index Class Name: REVISION
• Doc Date: 12/19/2008
• Doc Name: Mod.- of Backfill Plan for Schist Island Mine-CONT.
• From: CC&V
• To: DRMS
• Type & Sequence: TR53
• Media Type: D
• Archive: No

•
C
PROJECT: FLOW FROM GLOBE HILL MINE TO SCHIST ISLAND MINE - MOD
AUTHOR: Adrian Brown, P.E. DATE: 11/1
PAGE: 3 3 OF 4
OF 4
ANALYSIS (continued)
Result of isotropic hydraulic conductivity analysis
The analysis indicates that for isotropic bedrock hydraulic conductivity, any water that seeps horizontally
out of the Globe Hill Mine toward the Schist Island Mine moves vertically into the diatreme before traversing
more than 1 % of the distance to overflow from the Schist Island backfill. This finding is independent of the
magnitude of the hydraulic conductivity of the diatremal bedrock.
Anisotronic hydraulic conductivity
The diatremal bedrock may not be isotropic; very low relative vertical conductivity favors lateral flow.
Consider the above analysis using a horizontal hydraulic conductivity of 100 ft/yr and variable anisotropy.
Evaluation is for the full range of anisotro for the Tertia Volcanics in the diatreme.
Vertical Hydraulic conductive of rock ft/ r 100 10
Horizontal h draulic conductive of rock fU r 1 0.62
100 100 100 100
Anisotropy Kh/Kv ratio 1 10 10i) 161
Compute vertical loss of flow during transit from Globe Hill towards Schist Island
Diatreme is unsaturated for approximately 3000 feet below GI and SI area
Any water entering the bedrock in this area is subject to vertical flow under gravity
Flow is computed from Darcy's Law
Q = Kv I A Kv = hydraulic conductivity I = hydraulic qradient
Vertical hydraulic conductivity (Kv)
Vertical hydraulic gradient (1)
Distance from GH pool to SI west tip (f
Width of lateral flow in rock (from CAD
Cross sectional area of flow GH>SI
Vertical flow loss from GH to SI
Evaluate lateral flow to SI frnm rw
0.62
1
2230
590
1315700
815734
11.6.
11.7 11.7
1389.3 2240.8
62% 100%
Result of anisotropic hydraulic conductivity analysis
The analysis indicates that no water can flow from the Globe Hill Mine, through the bedrock wall to the
backfilled Schist Island Mine, across the backfill, and over the bedrock lip to the accessible environment
for any hydraulic conductivity anisotropy less than 161:1 (horizontal to vertical).
CONCLUSION
1 Globe Hill Mine will remain un-backfilled after Amendment 9, and will have no surface flow outlet
for incident precipitation.
2 The mine will temporarily collect water after a major precipitation event, due to internal ruoff.
3 DRMS is concerned that collected rainwater will seep laterally from the Globe Hill Mine through
approximately 1000 feet of rock and emerge in the highwall of the Schist Island Mine, potentially
causing groundwater quality impacts within that mine.
4 This possibilty has been evaluated by analysing the flow that would result from a maximal
precipitation event (12 inches of precipitation in 24 hours).
5 Groundwater flow from the Globe Hill Mine to the Schist Island Mine will not occur in isotropic
hydraulic conductivity rock.
6 Groundwater flow from the Globe Hill Mine to the Schist Island Mine can only occur when the
horizontal hydraulic conductity of the rock exceeds 100 times the vertical hydraulic conductivity.
A = area of flow
ru r 100 10 1'
ft/ft 1 1 1
It 2230 2230 2230
It 590 590 590
s .ft. 1315700 1315700 13157001
cuft/ r 1131570000 13157000 1315700
m 1872 187 18.7
Flow from SI to GH

Distance of penetration towards SI from GH m
ft 11.7
13
9 11,7

Percentage of total distance GH-SI covered
% . 138.9
1% 6%
Adrian Brown Consultants, Inc., 130 West Fourth Avenue, Denver, Colorado ;03-698-9080