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• contain 10 -year 24 hour storm even runoff from pond 006 and 007 drainage areas, a total of 6.6 <br />acre -ft. In addition, the Universal Soil Loss Equation was used to estimate sediment yield from <br />these areas at 0.3 acre -ft/yr (0.9 acre -ft for 3 years) at a conservative 1.0 sediment delivery ratio. <br />The total required capacity for Pond 007 is therefore 7.5 acre -ft. As shown by the stage volume <br />curve for Pond 007, 9.2 acre -ft of storage is available in Pond 007, allowing a surplus of 1.7 <br />acre -ft. The emergency spillway is adequate for passing peak 25 -year 24 -hour flows from both <br />drainage areas while maintaining 1 foot freeboard. Exhibit 19, Section 1 contains SedCad <br />documentations that indicate Pond 005 and Pond 007 can be operated with the gate valves open <br />and that sediment effluent limitation can be met. However, precipitation events sampled in 2003 <br />indicate that under current conditions, effluent limits at Pond 007 may be exceeded. Thus the <br />operator will operate this pond with the gates normally closed, until such time as it can be <br />demonstrated, either by maintenance or reclamation practices, that effluent limitations will be <br />met. All 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 perforated riser at <br />each pond under existing subwatershed conditions that had been previously analyzed in the <br />permit. The data used in this analysis, including watershed area calculations, was taken from <br />calculations performed for the design specification of Pond 5 and 7 in Exhibit 19 of the permit. <br />The drainage areas map in Exhibit 19 shows the watershed drainages for ponds 5 and 7. <br />Drainage area 005 -1 is the total drainage area for Pond 005. Drainage areas 006 -1 through 006 -5 <br />and 007 -1 through 007 -6 all constitute the total drainage area for Pond 007. The operator will <br />also open the gates on all other sites. A staff gage will be installed on or adjacent to the riser <br />pope of Pond 007 identifying the water level (7373.3 ft) adequate to retain a 10 -year 24 -hour <br />• storm without discharging over the emergency spillway. This elevation was arrived at through a <br />review of the Pond 007 as -built stage volume curve dated 5/31/85 in Exhibit 19. The crest <br />invert emergency spillway volume is 9.2 acre feet and the 10 -yr 24 -hr runoff volume is 6.6 acres <br />feet, resulting in an allowable permanent storage and sediment volume of 2.6 acre feet. <br />The operator has received approval from CDPH &E, Water Quality Control Division to use a <br />flocculent to settle suspended solids in pond water during emergency situations of for water <br />discharges associated with pond cleaning activities. <br />All materials removed through the cleaning or excavation of sediment and/or treatment ponds <br />will be disposed of at the development wastes pile according to approved Minor Revision 24. <br />TR 54 Page 2.05 -10a Revised 1 -3 -2011 <br />