2012-01-05_REVISION - C1980005 (8)

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reclamation activities at the Seneca II Mine site has been made by the applicant and is found in Volume 4, Tab 7, Section VII.B and Volume 14, Tab 2.04.7 of the permit application. This section includes an evaluation of quantity and quality effects on ground and surface water systems and mitigative measures to be taken both during and after mining. The Probable Hydrologic Consequences section of this document is divided into two main subsections: Surface Water Effects and Ground Water Effects. Surface Water Effects The Seneca II Mine is located in the upper Yampa River basin on the north flank of the Williams Fork Mountains. The mine is located on a watershed divide between the Fish Creek drainage basin to the east and the Grassy Creek drainage basin to the west. Most of the previous mining at the original site occurred in the Little Grassy Creek basin which is tributary to Grassy Creek, a perennial tributary to the Yampa River. Mining in the Fish Creek basin began in 1982, in the Cow Camp Creek tributary basin. As mining in this drainage was completed, an area in another tributary basin of Fish Creek, Bond Creek, was disturbed; the disturbance area in Bond Creek comprises the current permit area. All mining activities have ceased and reclamation is nearly complete. The effects of mining on the water quality and quantity in the Fish Creek Basin are discussed below. Fish Creek Drainage Basin Mining in the Bond Creek drainage began in 1988. Flow from pond 008 peaked from 1995 -1999, and has since decreased and is approaching pre -mine rates. Mean annual flow in 1987 was .028 cfs, and in 2009 it was 0.112 cfs. Concentrations of total dissolved solids increased steadily from July values of 530 mg /1 in 1988 to 3,600 mg /1 in 2007, but have showed a decreasing trend since. The level was 2,850 mg /1 in July 2010. Fish Creek is monitored at site SW- S2 -13, downstream of the confluences of Bond Creek and Cow Camp Creek with Fish Creek. Data from the site does not show any identifiable change in water quality or quantity when compared with Fish Creek site SW- S2 -11, upstream of Bond Creek and Cow Camp Creek. Effects of Mining on Surface Water Changes in the quantity of water to the prevailing hydrologic balance are primarily due to the location and timing of flows. The Fish Creek drainage indicates a change in the ground and surface water systems. Mining has increased the amount of ground water available to be discharged into the surface water system, due to discharging spoil aquifers. Cow Camp Creek now exhibits perennial stream flow as a result of mining in this drainage whereas prior to mining the 16