Laserfiche WebLink
~~ An artificial form of recharge is occurring as a result of the irrigation ditch network and <br /> practices in the immed iate vicinity of the mine. Were there not this source of recharge, <br /> the time required for the spoil to recharge from natural ground water flan and rainfall <br /> would be considerably longer. In conclusion, the mining operation will not diminish <br />vertical or horizontal permeabilities and may increase them, thus there should be no <br />significant impacts from the mining operation on ground water flow and recharge rates. <br />The time period required for the spoil material to resaturate should be greatly reduced <br />because of all the irrigation recharge (the Nucla East area wilt be revegeta ted for an <br />irrigation type of postmining }and use). <br />Containment of Pit Inflow Pumpage and Impacts on Water Quality. All runoff and pit <br />pumpage from disturbed areas are routed through sedimentation ponds. The ponds are <br />designed and constructed to impound runoff and pit pumpage from areas disturbed by mining <br />and provide sufficient residence time to insure that the pond discharge water chemistry <br />meets the effluent requirements~specif ied in NPDES Permit No. CO-0000213 (see Tab 7, <br />Appendix 7-6). Plans have been developed for water rights augmentation pumping from the <br />ponds and minimizing erosion during the pumping (pages 73-6 and 13-70 in Tab 13). In <br />• total, seven NPDES ponds are or will be constructed to contain runoff and pit pumpage from <br />the two mining areas. Ponds 001 through 006 receive all runoff and pumpage from the Nucla <br />mining area and Pond 007 is proposed to contain all discharges from the Nucla East mining <br />area. To date, Ponds 002, 003, 004 and 005 have never discharged. All flow data for Pond <br />001 can be found in Tab 7, Appendix 7-5. Appendix 7-7 of Tab 7 presents all chemical data <br />for discharges and monitoring at Ponds 001 and 006 as well as ail flow data for 006. <br />A review of the chemical and flow data indicates that the potential for any discharge from <br />Pond 007 to exceed state receiving stream or federal standards is very minimal. Through <br />1987, only one NPDES standard has been exceeded at Ponds 007 and 006. The exceedence <br />occurred in 7982 at Pond 001, The measured 30 day average for T55 was 45 mg/1 and the <br />NPDES standard is 35 mg/1, Also, there has been only one exceedence of the Colorado <br />Department of Health receiving stream standards for Segment 5 of the San Miguel River. A <br />total recoverable value of 140 ug/7 for Ni was measured in the discharge from Pond 001 and <br />the receiving stream standard is 100 ug/1. The significance of this is negligible as <br />there is no Ni standard for Tuttle Draw, the associated flow was small and the impact to <br /> the higher flow San Miguel water quality would not be measurable. <br />~'~ <br /> In the pit inflow section of this Tab, rates of ground water inflow by year have been <br />calculated. The highest rate of inflow is projected to occur in year 5 of the Nucla East <br />17-29 Revised 08/19/88 <br />