Laserfiche WebLink
• <br /> <br />PROJECT: FLOW FROM GLOBE HILL MINE TO SCHIST ISLAND MINE - MOD DATE: 11/19/2008 <br />AUTHOR: Adrian Brown, P.E. PAGE: 3 OF 4 <br />ANALYSIS (continued) <br />Result of isotropic hydraulic conductivity analysis <br />The analysis indicates that for isotropic bedrock hydraulic conductivity, any water that seeps horizontally <br />out of the Globe Hill Mine toward the Schist Island Mine moves vertically into the diatreme before traversing <br />more than 1 % of the distance to overflow from the Schist Island backfill. This finding is independent of the <br />magnitude of the hydraulic conductivity of the diatremal bedrock. <br />Anisotrooic hydraulic conductivity <br />The diatremal bedrock may not be isotropic; very low relative vertical conductivity favors lateral flow. <br />Consider the above analysis using a horizontal hydraulic conductivity of 100 ft/yr and variable anisotropy. <br />Evaluation is for the full rannP of AniSnfrnn., fir fk. re.4c--, %v.i_. - :-- :_ <br />- -- ---•--••_ .... .. .. <br />Vertical Hydraulic conductive of rock . ,a.,um vv <br />ft/ 01JI'a 11 1 UIV Uldll erne. <br /> <br />Horizontal hydraulic conductive of rock r <br />f / r 100 <br />100 10 <br />100 1 0.62 <br /> <br />Anisotropy Kh/Kv <br />ratio <br />1 <br />10 100 <br />100 100 <br />161 <br />Compute vertical loss of flow during transit from Globe Hill towards Schist Island <br />Diatreme is unsaturated for approximately 3000 feet below GI and SI area <br />Any water entering the bedrock in this area is subject to vertical flow under gravity <br />Flow is computed from Darcy's Law <br />Q = Kv I A Kv = hvdralilie, rnnrh irfivif., <br />Vertical hydraulic conductivity Kv ft/ ' _ " u' rauient A = area o1 now <br /> <br /> <br />Vertical hydraulic gradient I r <br /> <br />ft/ft <br />100 <br />1 <br />10 <br />0.62 <br /> <br />Distance from GH pool to SI west lip fr. CAD <br />ft <br />2230 1 <br />2230 1 <br />2230 1 <br />2230 <br />Width of lateral flow in rock from CAD ft 590 590 <br /> <br />Cross sectional area of flow GH>SI A <br />sq. ft. <br />1315700 <br />1315700 590 <br />1315700 590 <br />1315700 <br />Vertical flow loss from GH to SI cufU r 131570000 13157000 1315700 815734 <br /> m 1872 187 18.7 11.6 <br />Flow from SI to GH m 11.7 11.7 11 <br />7 11 <br />7 <br />Distance of penetration towards SI from GH ft 13.9 138.9 . <br />1389.3 . <br />2240 <br />8 <br />Percentage of total distance GH-Sl covered % 1 % 6% 62% . <br />100% <br />Evaluate lateral flow to SI from GH <br />Result of anisotropic hydraulic conductivity analysis <br />The analysis indicates that no water can flow from the Globe Hill Mine, through the bedrock wall to the <br />backfilled Schist Island Mine, across the backfill, and over the bedrock lip to the accessible environment <br />for any hydraulic conductivity anisotropy less than 161:1 (horizontal to vertical). <br />CONCLUSION <br />1 Globe Hill Mine will remain un-backfilled after Amendment 9, and will have no surface flow outlet <br />for incident precipitation. <br />2 The mine will temporarily collect water after a major precipitation event, due to internal ruoff. <br />3 DRMS is concerned that collected rainwater will seep laterally from the Globe Hill Mine through <br />approximately 1000 feet of rock and emerge in the highwall of the Schist Island Mine, potentially <br />causing groundwater quality impacts within that mine. <br />4 This possibilty has been evaluated by analysing the flow that would result from a maximal <br />precipitation event (12 inches of precipitation in 24 hours). <br />5 Groundwater flow from the Globe Hill Mine to the Schist Island Mine will not occur in isotropic <br />hydraulic conductivity rock. <br />6 Groundwater flow from the Globe Hill Mine to the Schist Island Mine can only occur when the <br />horizontal hydraulic conductity of the rock exceeds 100 times the vertical hydraulic conductivity. <br />murian rsrown consultants, Inc., 130 West Fourth Avenue, Denver, Colorado <br />303-698-9080