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East Pit watershed and roughly 285 acres will be in the Streeter watershed, compared to Colowyo's estimate of 100 acres of disturbance in the East Pit Watershed and 50.6 acres in the Streeter watershed. As you can see, the umbers derived by the Division are substantially different from what was estimated by Colowyo. The Division understands the difficulty in estimating the "worst-case" situation at the end of mining each pit. The Division, therefore, will approve the acreages estimated by Colowyo in order to convert the ponds from a "containment structure" to a "treatment structure" However, at the 5-year permit term, prior to closure of the pit, the Division will require Colowyo to reevaluate the sediment pond designs with a more precise reclamation plan. The Division proposes to add a stipulation to the TR approval; PRIOR TO THE 5-YEAR PERMIT TERM WHERE THE FINAL PIT WILL CLOSE (EAST PTT, WEST PIT AND SECTION 16 PTT), THE OPERATOR WII.I. REEVALUATE ALL SEDIMENT PONDS WTI'fIIIV THE PTT WATERSHED BOUNDARIES TO DETERMINE THE WORST-CASE DISTURBANCE AND THE TIMING OF RECLAMATION. THIS EVALUATION SHALL BE SUBMITTED AND APPROVED BY THE DMSION. 2. On Table 5 titled, Sedimentation Pond Data Summarv, Colowyo lists the predicted annual sediment loading (acre-feet) and the available sediment storage volume (acre-feet). The SEDCAD+ model contains a sediment capacity based on average annual R of 19.0 for 1.0 years. Colowyo estimates the predicted number of storage yeazs based on the predicted and available sediment storage volume. The SEDCAD+ model is only designed for 1.0 yeazs of sediment storage. If Colowyo wishes to accumulate more sediment in the pond than the predicted volume, then the SEDCAD+ model needs to reflect the anticipated sediment volume. Please revise the SEDCAD+ designs accordingly to demonstrate that the "treatment pond" will function with the available sediment storage volume estimated by Colowyo in Table 5. 3. The Division compazed the new elevations of the primary spillway, emergency spillway, and top of embankments to the old design "as-builts." There is, in general, a discrepancy with the pond elevations. Please provide the Division with pond diagrams including all of the revised changes to the spillways. This is necessary in order for the Division to complete its review of the sediment pond's modification. 4. In a majority of the sediment pond designs, the peak flow has increased for the 25-year, 24-hour storm event. Colowyo needs to demonstrate that [he emergency spillways and inlet ditches to the pond will be able to safely pass the predicted runoff. Please provide the Division with demonstrations that the emergency spillway will safely pass the peak flow from the 25-year, 24-hour storm event. Please also provide the Division with designs for the inlet ditches to the sediment ponds. 5. As noted previously, the peak flow for the 10-year and 25-year events has increased. As result of this review, the Division believes that all permanent and temporary diversions should be reevaluated. The Division does not wan[ to delay the approval of this revision, and the modifications [o [he sediment ponds in light of spring run off. Therefore, the Division will add a