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100 90 80 70 60 50 �R 40 30 20 10 0 Seneca IIW Sagebrush Reference Area Corer Data 200E 2067 2009 2011 2012 Year Veg cover #Ground cover Annual cover 9b. The division requested analysis which compares suspended solids generated off the pre- mining land to the bond release area. Table 17 -25 on page 68 in Tab 17, Probable Hydrologic Consequences of the Seneca II -W Permit Application Package shows Peak Sediment Concentrations predicted by SEDIMOT II, the precursor to SEDCAD for Pond 006 (shown below). These runs remain useful considering that recent pond capacity surveys in Pond 006 from 2009 through 2013 show negligible sediment accumulation over a five year period as seen on the graph for Pond Capacity Table for Pond 006 (above for response to 9a). The above graphs for Ponds 005, 009, and 016 also show negligible sediment accumulation over the last three years (2011 through 2013). Modeling showed both the pre and post - mine conditions contribute very small sediment loads compared to the condition during mining when there was little or no vegetation present above the pond. Furthermore, the original modeling results indicated minimal erosion would occur once reclamation is completed above both Ponds 005 and 006 due to a predicted increase in runoff The capacity surveys on Pond 006 and the other three ponds support this prediction, and also show sufficient treatment (detention time) has been maintained in these ponds prior to the eventual discharge from the impoundment outfall. Peak Discharges Runoff Volume, Peak Sediment Concentration and Sediment Yield Calculated Using SEDIMOT II for the 005 and 006 Gulch watersheds Peak Runoff Peak Sediment Sediment Watershed Condition Storm Discharge (cfs) Volume (ac -ft) Concentration (m 11) Yield (tons) 0051 Premising 10 yr -24 hr 0.00 0.00 0.00 0.0 2 005 Postmining 10 yr -24 hr 0.20 0.123 8,66 0.0013 0051 Premining 100 yr -24 hr 0.31 0.259 8,10 0.0022 0052 Postmining 100 yr -24 hr 6.41 7.52 20.2 0.0453 006 Premining 10 yr-24 hr 0.05 0.020 8.45 0.0002 4 006 Postmining 10 yr -24 hr 0.98 0.665 9.12 0,0073 0063 Premining 100 yr -24 hr 2.04 1,52 60.7 0,0760 0064 Postmining 100 yr -24 hr 26.4 11.7 22.8 0.2319 1 Total drainage area = 198.4 acres 2Total drainage area = 196.9 acres 3 Total drainage area = 725.3 acres 4 Total drainage area - 729.9 acres These runs remain useful considering that recent pond capacity surveys in Pond 006 from 2009 through 2013 show negligible sediment accumulation over a five year period as seen on the graph for Pond Capacity Table for Pond 006 (above for response to 9a). The above graphs for Ponds 005, 009, and 016 also show negligible sediment accumulation over the last three years (2011 through 2013). Modeling showed both the pre and post - mine conditions contribute very small sediment loads compared to the condition during mining when there was little or no vegetation present above the pond. Furthermore, the original modeling results indicated minimal erosion would occur once reclamation is completed above both Ponds 005 and 006 due to a predicted increase in runoff The capacity surveys on Pond 006 and the other three ponds support this prediction, and also show sufficient treatment (detention time) has been maintained in these ponds prior to the eventual discharge from the impoundment outfall.