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September 18, 2001 <br />Page 2 of 3 Pages <br />to be 6.46 cubic feet per second. The peak sediment concentration in the effluent from such an <br />event is demonstrated to be 39,301 milligrams per liter, and the peak settleable concentration is <br />demonstrated to be 0.00 milliliters liter. The design capacity of this pond is 2.20 acre feet of <br />sediment and water prior to initial discharge. At full design sediment storage of 0.84 acre feet, <br />the pond is designed to hold 1.36 acre feet of water at initial discharge. <br />By reference 3), Colowyo reports that a 1998 survey of Streeter Pond indicated a capacity to <br />contain 2.6252 acre-feet of water prior to discharging. This capacity indicates a clean and over- <br />excavated (or over-sized) pond by 0.4252 acre feet. A storage volume of 1.3424 acre feet was <br />found in the (Colowyo) June 2001 survey. The sediment level in the June 2001 survey was thus <br />reported as slightly over design maximum level (a capacity of 1.34 verses the design 1.36). The <br />Division inspection (reference 6) of September 12, 2001 collaborates this report. This pond is <br />scheduled for dredging later this month (reference 6, September 12, 2001). <br />The Stoker Siding Pond (Outfall OOSA) <br />This pond appeazs to have had capacity prior to the event. <br />This pond has a design capacity (reference 5, Exhibit 7, Tab 13, Appendix E, 04-17-1998) of <br />0.02 acre feet of sediment storage and 0.68 acre feet of water storage at the stage of peak <br />discharge from a ] 0-year - 24 hour event. The peak discharge of such an event is demonstrated <br />to be 0.49 cubic feet per second. The peak sediment concentration in the effluent from such an <br />event is demonstrated to be 9,597 milligrams per liter, and the peak settleable concentration is <br />demonstrated to be 0.00 milliliters liter. The design capacity of this pond is <br />0.37 acre feet of sediment and water prior to initial dischazge. At full design sediment storage of <br />0.02 acre feet, the pond is designed to hold 0.35 acre feet of water at initial discharge. <br />By reference 3), Colowyo reports that a 1998 survey of this Stoker Siding Pond indicated a <br />capacity to contain 0.3005 acre-feet of water prior to dischazging. This capacity indicates that <br />there was more sediment in the pond than the design maximum volume by approximately 0.05 <br />acre feet. By this same Reference 3), Colowyo states that sediment was removed from the pond <br />in September of 1998 (the pond was cleaned or dredged) to where there was more than the <br />original design capacity, and that the current storage volume was 0.6268 acre-feet (water storage <br />to initial discharge). <br />The Rail Loop Pond (Outfall 006A) <br />The information available is insufficient to demonstrate that there was capacity prior to the <br />event. <br />This pond has a design capacity (reference 5, Exhibit 7, Tab 13, Appendix F, 04-17-1998) of <br />0.02 acre feet of sediment storage and 1.16 acre feet of water storage at the stage of peak <br />