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Sedimentology <br />In the application for the SL -05 bond release, SCC provided TSS data for five years of discharges <br />from five ponds (006, 009, 015, 016, and 017). This data indicates that average concentrations for <br />all five of the ponds, over the five -year period, did not exceed the monthly exceedance limit of 35 <br />mg /1 listed in the Colorado Discharge Permit System (CDPS) permit for Seneca II -W. While this is <br />a comparison of a five -year average to a criterion for a monthly average, it provides an acceptable <br />measure of the chronic condition of TSS concentrations from the ponds. SCC also provided a <br />comparison of discharge data to the maximum CDPS limit of 70 mg /1, and no exceedances were <br />reported. <br />While this information was useful, it did not completely meet the requirements of Rule 3.03.1(3)(b), <br />which states that, "No more than sixty (60) percent of the bond shall be released so long as the lands <br />to which the release would be applicable are contributing suspended solids to streamflow or runoff <br />outside the permit area in excess of premining levels as determined by baseline data or in excess of <br />levels determined on adjacent nonmined area." Therefore, the Division requested the following <br />from SCC: <br />• TSS data for Pond 005, since this data was omitted from the original submittal while data <br />for other ponds was submitted. <br />• TSS data for Sage Creek upstream of points 015 and 009. This data would allow the <br />Division to assess the assertion that TSS concentrations in the creek above the mine are <br />higher than concentrations in discharges. <br />• To assess sediment loading from the reclamation areas related to SL -05, the Division asked <br />for: <br />• Pond capacities based on survey data. <br />• An analysis using a predictive model, such as SEDCAD or RUSLE, which <br />compares the suspended solids generated off the pre - mining land or comparable <br />adjacent areas to the bond release area. <br />In response to the Division adequacy comments, SCC provided the following: <br />• TSS data for Pond 005 showing that CDPS criteria (average and maximum) were not <br />exceeded for this pond. <br />• TSS data for Sage Creek upstream of points 015 and 009. This data shows that TSS <br />concentrations in the creek above the mine are significantly higher than concentrations in <br />discharges. <br />• Pond survey data showing that sediment loads to the ponds have been very small in the past <br />five years. <br />• Vegetation data showing that ground cover values are good, leading to reduced erosion in <br />the watersheds. <br />Page 13 of 18 <br />