APPCOR13017 - Laserfiche WebLink

Home Browse Search

-4 e~ 7. Due to the potential for full saturation of the backfilled mine pits near '^ ~~'ti~, the toes of the pits, the applicant should instigate a monitoring program to ~lY ~~It~i visually inspect the areas near the toes of the reclaimed mine pits for 4~, evidence of springs or seeps emanating from the pits. If this Inspection ~ ~,(~~~.1,- program reveals the existence of springs or seeps, they should be monitored f1~ for flow rate, duration of flow, and water quality parameters 1n consultation ~ ~~ with the Division. The visual Inspection program should be conducted on a y monthly basis, except when snow-pack cover prohibits tt. All results of this Inspection and monitoring program should be included in the applicant's annual hydrologic reports to the Division. The Probable Hydrologic Consequences section of the permit application is divided into two main subsections: Ground Nater Effects and Surface Mater Effects. The following comments and questions are addressed under these headings. A. Ground Water Effects ,, 1. Dewatering It is stated on pages 2.06-165 and 166 that existing data and field ~ ~ observations of the existing pits at Mtne No. 3 substantiate that surface `i~ ~~-' mining has not in the past, and is not expected to 1n the future, dewater the ~'.! ~ overburden aquifer under the proposed mining plan. Therefore, no drawdown of IJ~ ';" water levels 1n the overburden aquifer is predicted from the surface I ~~ operations. However, 1t is stated on page 2.05-168 that the increased rate of ~ ' ,~I~' recharge of the reclaimed spoils material will enable rapid recovery of the ~` ` original storage volume of the undisturbed overburden aquifer from the y~~ tempo.~y_dewatering due to mining. These conflicting statements should be revised to clarify this situation with regard to dewatering of the overburden rr~ ~d }~~p/yl y~liU y~scr aquifer. ~ u ~ 2. Recharge Capacity The post-mining recharge rate of the overburden aquifer in the Mine No. 3 area was estimated by the applicant to be 140 acre-feet/year as compared to the recharge rate of 9.0 acre-feet/year For the overburden aquifer in the 1 Iv" pre-mining condition (page 2.05-167). This raises the question of water ~ i iur balance. The applicant states that water infiltrating Into the backfilled ~ ~d, mine pits will flow downslope to the highvall where tt will provide recharge to the undisturbed overburden aquifer. Supporting calculations are needed to verify that the undisturbed overburden aquifer 1s capable of transmitting this Increased volume of recharge water, so that spoils water from the reclaimed pits does not eventually discharge from the toe of the pits to the surface water or shallow alluvial aquifer systems.