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22 <br />three years of sediment storage between 0.98 and 1.28 acre -feet. The Operator <br />retains the option to use all 4.03 acre -feet as a combination of sediment or permanent <br />pool storage. Sediment would be cleaned out at an elevation of 7,449 feet. The <br />Operator periodically stores drilling fluids in this pond to the elevation of the lowest <br />dewatering orifice and, depending on existing water storage in the pond, there would <br />be a maximum of 2.75 acre -feet (895,950 gallons) of fluids in this pond. The <br />duration of storage will depend upon the quality of the pond's water and the size of <br />subsequent storm events. This pond is a permanent impoundment on Colorado Parks <br />and Wildlife lands. Once drilling fluids have dried, and the pond is dry, the operator <br />will selectively clean the dried material from this pond and transport to DWDA #2 or <br />DWDA #3 for permanent disposal. The operator will take care to leave as much of <br />the vegetation as possible in this pond during any sediment removal operations. <br />The Operator constructed the preparation plant in the spring of 1984. After several <br />months of operation, it was determined that a plant process pond was required to <br />accommodate plant discharges. The Operator submitted a permit revision whereby <br />Pond 006 was taken out of the surface drainage plan and modified to a plant process <br />pond. Pond 007 was sufficiently oversized to handle the additional runoff formerly <br />reporting to Pond 006. <br />Exhibit 19- Sediment Design Specifications and West Portal Drainage Plan, <br />confirm that Pond 007 (as- built) has sufficient storage capacity to contain 10 -year, <br />24 -hour storm event runoff from pond 006 and 007 drainage areas, a total of 6.6 acre - <br />feet. In addition the Universal Soil Loss equation was used to estimate sediment <br />yield from these areas at 0.3 acre - feet/year (0.9 acre -feet for three years) at a <br />conservative 1.0 sediment delivery ratio. The total required capacity for Pond 7 is <br />therefore 7.5 acre -feet. Construction of the Bates Portal will add in incremental <br />amount of water (0.21 acre -feet) and sediment (0.01 acre -feet) to pond 7. Therefore <br />the required storage volume for sediment pond 007 is 7.7 acre -feet. As shown by the <br />stage volume curve for Pond 007, 9.2 acre -feet of storage is available in Pond 007. <br />The emergency spillway is adequate for passing peak 25 -year 24 -hour flows from <br />both drainage areas while maintaining 1 -foot freeboard. Exhibit 19, Section 1 <br />contains SedCad documentations that indicate Pond 005 and Pond 007 can be <br />operated with the gate valves open and that sediment effluent limitation can be met. <br />However, precipitation events sampled in 2003 indicate that under current conditions, <br />effluent limits at Pond 007 may be exceeded. Thus the operator will operate this pond <br />with the gates normally closed, until such time as it can be demonstrated, either by <br />maintenance or reclamation practices, that effluent limitations will be met. All <br />sampling during discharge events will be conducted in accordance with the approved <br />NPDES permit to determine actual compliance with limitations. <br />The SedCad analysis for Ponds 005 and 007 was an analysis of an installed <br />perforated riser at each pond under existing sub watershed conditions that had been <br />previously analyzed in the permit. The data used in this analysis, including <br />watershed area calculations, was taken from calculations performed for the design <br />specification of Pond 5 and 7 in Exhibit 19 of the permit. The drainage areas map in <br />Exhibit 19 shows the watershed drainages for ponds 5 and 7. Drainage area 005 -1 is <br />the total drainage area for Pond 005. Drainage areas 006 -1 through 006 -5 and 007 -1 <br />Section 2.05 TR -68 12/10/2014 <br />