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below, an application has been made to the State Engineer's Office for each <br />• impoundment. <br />The applicable hydrologic/hydraulic design criteria are those found at 4.05.9 (7) and <br />4.05.9 (2) (c) (ii), which require a minimum freeboard of one foot when passing the <br />specified 25 year 24 hour design storm, and 4.05.9 (2) (a) (ii) which requires spillway <br />and outlet channel linings adequate to resist erosion when passing the design storm. <br />The applicable slope steepness limits are found at 4.05.9 (7) (e) which requires combined <br />upstream and downstream slopes to be no steeper than 5H:1 V and neither slope steeper <br />than 211:1 V. <br />The applicable numerical slope stability requirement is at found at 4.05.9 (8) (b) which <br />requires a minimum static slope stability safety factor of 1.3 in the steady state seepage <br />condition under full reservoir pool. <br />Engineering analyses demonstrating that all of the above criteria are satisfied have been <br />performed as described in the following paragraphs, and pertinent results are presented in <br />Table 1. <br />Detailed Discussion of Factors Addressed in the Regulations <br />• For clarity and ease of review, these and other topics required in the regulations for the <br />demonstration seeking approval of permanent impoundments are addressed in the order <br />that they appear in the regulations. This arrangement may at times be redundant to the <br />extent that related topics are sometimes addressed in several locations in the regulation. <br />4.05.2 (a) (ii) Grass lined spillway adequate to carry short term infrequent flows at <br />non - erosive velocities <br />The spillways of all of the stock tanks are grass lined. Routed storm outflow for each <br />stock tank was determined using the program SEDCAD as described in more detail <br />below, with the SEDCAD output files presented here in Appendix D. With the routed <br />outflow from the 25 year, 24 hour storm as determined with SEDCAD, flow velocities in <br />the control section of each spillway were then determined by dividing that storm outflow <br />by the wetted cross sectional area of the spillway. The wetted cross sectional area was <br />arrived at by using the flow depth determined in the SEDCAD modeling and the <br />emergency spillway channel dimensions. Control section velocities so determined are <br />presented in Table 1. It can be observed that in all cases the flow velocity is less than 2 <br />ft /sec, well below the 5 ft/sec threshold of damage generally applicable to grass lined <br />channels. ( Ref. i) The flow velocity in the outlet channel was then determined by solving <br />Manning's equation for the above described routed outflow and the outlet channel slope <br />and dimensions as determined from the as -built topographic maps presented on Figure 1. <br />U <br />Exh. 7 -13 -4 Revision No.: TR -89 <br />Revision Date: 02/11/11 <br />