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ID~3037638003 <br />NO'J 12'98 15 55 No .005 P.02 <br />HYDROLOGIC' .+'•n UL•'SIGN llbCa1MF.NTATION <br />DRTI.f-T'At ~ .MALL ARL'A IiXT=.MPTTpN <br />PUI ~ HiT. Ckh.1iK MINL <br />lN'I'KODUC'I'ION <br />Thc (ollowing hydrologic and dasign tlucunxm;+tiun is provided to support;, .mall area exemptiim (JAL•') <br />Ibr tha drill pad and cuntainmcm berm oulslopv` inras. '1'wcntymrlc ('nal Mine (lwentymilu) pntposcs to <br />cnn<tntcl a 2 foot high bum (witlt 2H:1 V slopes) to contain Ihi+ runul I' I'rum the drill pail mtd li, !real runoff <br />from the cnmainment bet7n oulclopc uliliiing a gran lihcr. ht ndtlitiml, runul'I which occur; Up-Fradicnt ul' <br />lhu drill pad will he. diverted away from the drill pad and treated (rill farce) pries' lu discharge. <br />Runofl'volwne calculations woo pi+rfurutcd wilizing the S~6GAU4 computer modal consistent with the <br />mulhodologics presented in previous subiniltrtls. ticdin,cnl yield calenlalions weru bused nn disturbed m'on <br />panicle sizo distributions presentud in previous subntinnls and shown on the accompanying SLllCA1J4 <br />computer prinlOUls, <br />I.0 Ib'ill 1'ad Arut <br />'I~he following calatL•diuns dumonslrate Ihat a 2-fool i'uulaiuntcnl berm constructed nrounil the proposed <br />drill pad area will cmm~in the runi,ff from a I(Yyrn/24-hoar (LR in) slonn oven!, which ncnus within tlu• <br />bcrnt. <br />iiydrolygy-liuwts <br />• Thc Cw've. Number (C1N) used fur the drill pad area was obtained from procedures for lletcnnining i'cak <br />Flows in Cnlarnrln and'I'echnical KUlcnsc No. 55. Thc curve number tuns dctermiucd for the following soil <br />and vegetation conditions: <br />I)istunc~rl <br />Snil'lypc; Cuulis B <br />Ground Cover: Distw'bctl <br />(::over'1'ypc: N/A <br />CN: Rb <br />All idhcr hydrology inputs arc shown nn the nuachcJ 5L'DCA1)4 cnmpma' printouts. <br />lydrningy Rcsuhs <br />Runoff Voluntr. O.U7 ac 1) <br />13cnn llcsign <br />A 2 ft high cuntnimncm berm will be eonslruelcil around the drill pad area with Chu south .eidc scgmem <br />buih along the contour fur n minimum of I(1(I fi. Su~il?piug of a minimum of I font of lupsitil IFum the drill <br />pad :uca will add ut additional foul of cuntaimncm height. Itnscd on topography supplirtl by'1'wcntymilc <br />C'ual Minu, dte slope nl the land up-gradian ul the wWhcrn berm section is 10°:F. l•hc .ztomge voluute. was <br />talculNed as follows: <br />C7russ~ sectional area (ennminnnem an:a): berm (2H:1 V .c(opes) , i 0 high, l5 ft length (1 lorii). <br />. IOr/n slope = .54 .cq. fl. <br />5tuntgu vulmnc: (54 sq. fr. X I CIO fl (berw length)) = 5400 cu. fl. = 0. I Z :4~'. ft. <br />I~R9~-161 <br />APPRpyE~ P1L;; i 2 1998 <br />