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minimum depth of 3 feet. Flow details of the several ditches under the three sequencing <br />time frames (2010, 2012 and 2017) as discussed below are presented in the attached <br />SEDCAD output printouts. In each ditch the maximum flow from the three reclamation <br />time frames was selected for the design flow. The peak 10 -year design flow for each <br />ditch is presented below, as well as the particular reclamation time frame that produced it. <br />• Prospect Ditch, maximum peak flow 13.4 cfs, from time frame 2010 <br />• N. Tributary, East Pit, maximum peak flow 26.8 cfs, from time frame 2010 <br />• Final East Pit Dutch, maximum peak flow 29.6 cfs, from time frame 2017 <br />As mentioned above, rip -rap is used for erosion protection in most reaches of all of the <br />ditches described in this section. Minimum stone size (1350) for each ditch was <br />determined in SEDCAD using the Simons /OSM model. The largest riprap size <br />determined in SEDCAD for any ditch and design flow is D50 > 6 inches. All ditches are <br />nevertheless designed with a minimum D50 of 12 inches. For channels with a vegetative <br />erosion control lining (upper reaches of Prospect Ditch, uppermost reach of North <br />Tributary East Pit Ditch) the maximum peak flow velocity for the design storm is 1.98 <br />fps (Prospect Ditch). This velocity is well below the maximum allowable velocity of 5 <br />fps for the vegetative cover lining. <br />Stock Ponds <br />In order to assure compliance with effluent requirements at the outlet of Prospect Pond, <br />up to 5 stock tanks will be constructed near the re- established main drainage channels of <br />Prospect Ditch, North Tributary East Pit Ditch, and Final East Pit Ditch. Three of these <br />(PD 1, PD2, and NTEP 1) will be constructed in 2010, one in 2011 (EP 1), and the other <br />(EP2) in 2012. <br />The stock tank ponds will be designed in accordance with Fig. 2.05 -6 "Stock Tank <br />Plan/Profile — Typical Design ", and constructed at the locations and reclamation time <br />frames shown on Figures Exh. 7 -14R -1 through Exh. 7 -14R -6 included in this technical <br />revision. In many cases these stock tanks completely intercept the runoff from their <br />tributary watersheds in the 10 year 24 hour design storm. Inlet and outlet details relating <br />to tie -in to their respective ditches are presented on Figure Exh. 7- 15R -8. <br />Three Reclamation Time Frames Evaluated <br />For the reclamation sequencing of the East Pit, three time frames were evaluated for the <br />drainage to Prospect Pond. The results of the SEDCAD modeling for each are described <br />below. Curve Numbers assigned to each subwatershed in each development stage are as <br />per TR -73. As would be expected, some of the curve numbers vary with the passage of <br />time as the age of the reclamation increases. <br />Spillway design storms for the Prospect Pond were included in Volume 2D, as previously <br />approved. <br />Exh. 7 -14R -2 <br />Revision Date: 11/3/10 <br />Revision No. TR -87 <br />