WPC  2"B Z`XArial ItalicArialArial BoldHP LaserJet 4 PlusIIHPLA4PLU.PRS2xCQ\'sZX#|9ND,C2xjAG;X1mC9,  Xm2PG;XP/qC:,cXq2pPG;X2n T|TOO "4^DDV6OOYAOAADDAwDADn6wD66w6RwDwwwuR?ROAnOOODOOOOOOuOAwCCCCCCCCwwwwwwA6AAA6AAgww6A6[6RRRwwwwTDDwuuu6RwDwwDu414WddddddddddddddddddddddddddddddddddddddddNTT~PYVPTO33PPPPTTyuu3OuO"uu~uu"m+^99Ipp.DDNt9D99pppppppppp99tttp̅}9ep}}999\p.ppepp9pp..e.ppppDe9peeeeE5EtD9sZDDD9DDDDDDpD|9pppppȰepppp99999999pppppppppepp|pepppppeeee|pppppppppppp9.999.99Xeep.p:p.pDp.pxppppȼDDDeeee}L}9}9ppppppe}e}e}epp.pDe}9ee|pp8dp,(,WddddddddddddddddddddddddddddddddddddddddNHxxHlpD|pppppLJpDHpD,,DDpDDxppxHxxHsdd,DdD"dxdldtxxd"m+^:D`pp8DDLt8D88ppppppppppDDttt|Đ|8p|||D8Dtp8p|p|pD||88p8||||LpD|pppdL8LtD8ttDDD8DDDDDDpD|8pppppȰppppp88888888|||||||||pp|||p||ppppppppppp||||||||88888888ppp|8|L|8|`|8|||||ȼLLLpppp|`|D|D||||||p|d|d|d||8|Lp|Dpp||:dp,0,WddddddddddddddddddddddddddddddddddddddddNHxxHppD|pppppLHpDPpD88ddpDDxppxHxxHs||8ddD"dxxldtxxd2  P #Xp2PQ XP#e  yxdddy Jicarilla Lower Mundo|'`v(#5Conceptual Design   III.XHYDROLOGIC DESIGN CRITERIA (#  R A.` ` Probable Maximum Flood (#` XX` ` The Probable Maximum Flood (PMF) is the maximum runoff condition resulting from the most severe combination of hydrologic and meteorologic conditions that are considered reasonably possible for the drainage basin study. The PMF for Lower Mundo Lake was determined to have a maximum inflow of 26,149 cubic feet per second (cfs).(#`  R B.` ` Inflow Design Flood XX` ` The Inflow Design Flood for Lower Mundo Lake Dam is equal to the Probable Maximum Flood, 26,149 cfs. The existing spillway will pass about 30% of the PMF before overtopping of the dam occurs. A modification to the structure must be made in order to bring the dam into regulatory compliance. Presently, the difference between the emergency spillway and the top of the dam is approximately 4.2 feet. Adding 1000 feet of similar concrete crest weir to the present 160foot length yields an elevation of 7330.4 during the PMF, 0.2 feet below the top of the dam. Alternately, if the dam were raised and the present spillway length unmodified, the maximum water surface elevation would reach 7337.0, 6.4 feet above the present top of dam. (#`  R C.` ` Development of Conceptual Improvements(#` XX` ` The Lower Mundo Lake Dam has inadequate spillway capacity to pass the inflow design flood. As noted in the Feasibility Design Report, the inadequate spillway capacity can be increased by raising the dam, widening the existing spillway, constructing an auxiliary spillway beyond the left abutment or allowing overtopping of a protected embankment. Five(,)) improvements were considered in the Feasibility Design Report to address the inability of the existing spillway to pass the inflow design flood without breaching the dam. Three of these improvements were not  , recommended for further study in this report; (1) raise dam crest to elevation 7339.5 with reinforced earth wall, (2) raise dam crest to elevation 7339.5 with reinforced concrete wall and (3) roller compacted concrete on downstream face for overtopping protection. Improvements (1) and (2) from above were not recommended primarily due to three reasons; (a) the steady state stability of the downstream slope of the existing embankment is below generally accepted values and thus the added weight to the embankment due to the reinforced earth or concrete wall without any downstream slope improvement would further act to reduce the steady state stability, (b) crest access for maintenance becomes a problem, and (c) annual operation/maintenance costs would most likely exceed those of the two improvements pursued in this report.(#` XX` ` The following two improvements were considered the most feasible for the conceptual design alternatives: (1) raise dam crest to elevation 7338 with earth embankment and (2) raise dam crest to 7336 with earth embankment and provide an auxiliary spillway. (#` XX` ` Raising the dam to elevation 7338 and leaving the existing spillway configuration intact would result in a maximum water storage elevation of 7337. A two foot parapet wall would be constructed on top of the dam to increase the freeboard to 3.0 feet.(#` XX` ` Raising the dam to elevation 7336.5 and providing an auxiliary spillway would result in a maximum water storage elevation of 7335.5. A two foot parapet wall would be constructed on top of the dam to increase the freeboard to 3.0 feet. (#` (,))ԌXX` ` For both of the raised embankment options the outlet pipe will be extended to the toe of the raised embankment and a riprap lined plunge pool will be provided. Also, the existing slide gate stem on the upstream slope will be modified to accommodate the raised embankment.