Laserfiche WebLink
Cresson Project Hvdroaeochemistry AdlianBrown <br />snowmelt and storm water runoff from these areas estimated as a maximum of 9.5 acre -feet per <br />year (Plate 14). The water is diverted to ground water, and ultimately flows from the Carlton <br />Tunnel. <br />2. After MLE2 Operations. All facilities within the additional areas encroached upon by MLE2 <br />shown on Plate 14 will be reclaimed by the end of site activities. It is expected that the storm <br />water runoff conditions will be similar to undisturbed grassland, which should provide <br />approximately the same runoff as the current landform. Accordingly, no incremental surface <br />water flow impact is expected after reclamation is complete. <br />2.6.3 Ground Water Flow Potential Impact <br />Potential ground water impacts due to MLE2 activities are as follows: <br />1. SGVLF Groundwater Interception. The principal potential impact to ground water flow <br />resulting from MLE2 activities will result from the installation of the liner system for the <br />SGVLF. The lined facility will be approximately 348 acres, and would prevent approximately <br />5.9 inches per year of infiltration. This represents a computed reduction in flow of the regional <br />ground water system at the Carlton Tunnel of approximately 171 acre -feet per year (106 gpm). <br />Accordingly, the potential impact of MLE2 on ground water flow is that the Carlton Tunnel <br />portal flow may reduce from its current rate of approximately 1,500 ± 1,000 gpm to <br />approximately 1,400 ± 1,000 gpm when the SGVLF liner system is completely laid. This <br />conclusion does not account for any potential changes in precipitation rate, which would not be <br />a result of MLE2 activities. <br />2. Groundwater Sequestration in Overburden. Uptake of infiltrating precipitation will potentially <br />occur as a result of MLE2 due to the sequestration of infiltrating water in overburden to reach its <br />field moisture content. The potential amount of sequestration of water is estimated as follows <br />(Appendix 3): <br />Facility Interception method Flow (gpm) <br />ECOSA Overburden Sequestration 71 <br />SGOSA Overburden Sequestration 71 <br />WHEX Backfill Sequestration 35 <br />Main Cresson Backfill Sequestration 58 <br />Total 235 <br />However this amount of flow reduction is not anticipated, due to the counterbalancing effect of <br />flow restarting in previously - placed overburden. The lack of any significant reduction in <br />diatremal outflow over the last 10 years during significant expansion of overburden volume <br />indicates that no further total flow reduction from this cause will occur. <br />3. After MLE2 Operations. After MLE2 operations, the liner systems of the valley leach facilities <br />( "VLFs ") will be breached, and the surfaces reclaimed At that time, recharge to the ground <br />water system will be restored and the Carlton Tunnel flow is expected to return to the pre - <br />mining rate of about 1,500 ± 1,000 gpm. <br />1385L.20120125 12 <br />