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Ditch 27 will direct runoff from Warehouse 1 to Containment Area 2. The total drainage area <br />is 2.9 acres. A total of 0.28-acre feet of storage is required to handle the 10-year 24-hour event <br />and 0.38 acre-feet of storage is required to handle a 25-year 24-hour event. The three-year <br />sediment volume is 0.02 acre-feet. Ditch 28 will direct disturbed runoff from a 15.45 acre <br />disturbed area to Containment Area 1. A total of 1.51 acre-feet of storage is required to handle <br />a 10-year 24-hour event and 2.01 acre-feet fora 25-year 24-hour event. The three-year <br />sediment storage volume is 0.07 acre-feet. Containment area 1 also controls drainage from the <br />non~oat waste disposal area. <br />Ditch 29 collects runoff from 67.2 acres of undisturbed runoff and directs this runoff to the <br />laydown area without impacting any disturbed area. Culvert C-27 has been installed at the east <br />end of the laydown area to handle peak flows from drainage basins CC and DD as shown on <br />Map 13A, Drainage Basin. - <br />Culverts-21 through C-25 direct undisturbed runoff south of the fan and substation to the <br />Purgatorie River. Sizing data is provided in Exhibit 19, Sediment Design Specifications. C-25 <br />was inspected and found to be draining all runoff adequately. WFC is unsure if it is a drop <br />structure or simple culvert. (It would be necessary to excavates the inlet to determine what type <br />of structure exits.) <br />• Pond 004 was surveyed in 1995 and found to have 7.19 acre-feet of volume. A 10-year 24-hour <br />storm of the contributing watershed is 0.9 acre-feet, a 25-year 24-hour storm is 1.13 acre-feet <br />and a 100-year 24-hour storm is 1.5 acre-feet. There was 3.78 acre-feet below the lowest <br />dewatering hole, of which SEDCAD+ estimates three years of sediment storage between 0.98- <br />1.28 acre-feet. Basin retains the option to use a114.03 acre-feet as a combination of sediment <br />or permanent pool storage. Sediment would be cleaned out at an elevation of 7449'. Basin <br />periodically stores drilling fluids in this pond to the elevation of the lowest de-watering orifice, <br />and depending on existing water storage in the pond, there would be a maxi.-num of 2.75 acre- <br />feet (895,950 gallons) of fluids in this pond. The duration of storage will depend upon the <br />' quality of the pond's water and the size of subsequent storm events. <br />WFC constructed the preparation plant in the spring of 1984. After several months of operation <br />it was determined that a plant process pond was required to accommodate plant discharges. <br />WFC submitted a permit revision whereby pond 006 was taken out of the surface drainage plan <br />and modified to a plant process pond. Pond 007 was sufficiently oversized to handle the <br />additional runoff formerly reporting to pond 006. <br />Exhibit 19, Sediment Design Specifications and Wes[ Portal Drainage Plan, confitr., that Pond <br />007 (as-built) has sufficient storage capacity to <br />• NE TR 40 2.05-10 Revised 10/16/95 <br />