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d ev:n 2: pre sent, pc ndin^ the ~c'e of th= :.~_
<br />d ~•ci.1 d^la preslwsl: reftn.'c to, man} r^:'~-.e~r:
<br />in lent u:•~. desi fined scdir•en[ ;. mall rrn.eo :r
<br />avid the -~~re ri ;, rous pro_e,ur_; r. q,:i red ~~
<br />M7n. da^•. ;.I :h ,uch ;his +~rov:o lc-er rh= ri s: o
<br />sl:^z faii;.res and conse4ue.^.tlv ir.'~ro rz safe ty ,r
<br />w']:~:r qu ]:i [) has ebviuusly suf fired.
<br />?h, Jrt[iC;~ G2 LC Minn Tine
<br />Ps 5-o..n in Table 2, ni ni -_~.-,+ "Ihro re[i[al de-
<br />t. r.;ion ;~~:'s" are specified `-)' Cb'1. Srcticn t'15.=j
<br />IC) Of t.n2 re gula[ions 5C2tes Cha l:
<br />"The o-e ticxl do tc nt;on tine is defined
<br />r. :h; peerage tine [hat ;he dasign `low
<br />is d~:ai r,ed in the pond; and is further
<br />de(ir5d as [he Lict dif fz re nGe to n~~een
<br />lh,u ce areid of [he ir.f!n~. Y.yd reg: aph
<br />and ;ha eentroid of the ou ;flo.: h)'dro-
<br />graph for the design even[."
<br />The re 7ula[ions reGUire a then rt tical dE [er;iop
<br />ti~.e of "not less than 24 hours, or any higYZr
<br />a~-ount reGui red by the regulatory au[ho ri [y". There
<br />ar- ^.c epticns ;o this, hn,.e ver. De [ention tir'ES ;
<br />r.,: Ic;s ;[ IC hours ^aY ba allc..ed if su R ici_-,
<br />tr cini;,al'ev ide nee is provided to justify Such eP
<br />re'uc [ion. Such evide nca would be in the fern of
<br />pr:,pesrd efficie^cY inpr ove~en[s (i.e., 6af`les,
<br />e (,.) and ana l'y [ical peon/ of achieving of fluent
<br />li-,i cations [hro..9h settling rate analysis sec so
<br />Fe rC,h. De ;ention [i.nas of any negni rude ray be
<br />apprc•:ed i( chemical trey [nzn[ is Croponed. Tne
<br />d^_sigaer Host de mn;[re [e that effluent limi to Cions
<br />.:ill be achieved and nain[ained, and also mcs[ cer-
<br />tify that :he ch e.^..i cnl agent er.pt eyed is anvir,n-
<br />r.:n[ally sa Fe. I; is s[re ssed throughout the regu-
<br />lations [Hat de [ention [uses alone do no[ nzcessar-
<br />ily assure compliance. Thz tot[en line is al+,~ays
<br />water quality.
<br />Desion Procedures
<br />Si^gle Da=Desion Under OSM
<br />A typical sed iren[ da.m in pro Fi le is sho~m in
<br />Figure I, and a [)'Dical plan vie++ in Figu rc 2. The
<br />'Ile' .[[ ^u^u^uuuiu
<br />4 ?d i:::cGi rJUI Ci!.= i5 C!rrr- III'll'II'll,'II'll
<br />999 _
<br />s;a]:~ ea :aci .. -+-^ zn^ the ~_. __ _ s, c. .
<br />vole T^c [J.^ cr _ ~,er .-. o:..~ ^;rv h: _.
<br />a[ 11lis CIC+a:iGn :.. ... .._.v lai= :^.P •t ~•:'-.
<br />liens n`cuire sE[ "K'`''r':: •'al C-cr c' - _
<br />r2i~a[.' J41Une .C .. __. (°_ _ le. _ T'), _
<br />VG L:''r Oi No(er ;r C•e :' ;'P. t^E ~'^;, -• sea''::-"
<br />pool and [he ores[ :i[E' .E d95`~'ale? in
<br />t^ii ra c,r di [he ',C :"L'~nL ~C C.1, iris wrllcr r_,
<br />or ray np; be slo.a) ro°eesed `: o^ the c;^ be;
<br />ra~n(,-,II even [>.
<br />Section °Ib.Lb(;) o% t^^ re;_latie-s sCa re:r
<br />'There shJll be no oa;rlo.. [`rC__^. the a-e rc rcy
<br />s;~i ll.:a'r durirr. [hr oa:5ect e` ._•. ru r. `.` resvtt[~.
<br />frva t6^ ID yc,:r/74 :,.. _•rc c:: ';a:i;,n ." Thrrt`e:e,
<br />Chr ir;i [ial s(eO in :`2 7ei1 yr: r'e ss 'S LO tC:l-
<br />stru;( tha 'unofi .`~, ._;~a?` for^;ne l:. year/2L
<br />hour .(fi rr: and roc :e.i; t-eau p'+ _ rlc_r ap _+ $ri~-
<br />P.u^o`f Hydroc: aphs
<br />The re are seve ra' to c•`.n iY:rs xvatleble to the
<br />des iynzr (or the construction of runoff ^.yd reS r:,p^s.
<br />Th_ ru^nff hydrogres'.s in this nonce ne re oenrrY cw
<br />ty u rG^p~[cr r.:~?cl [oat •-_. [he S-il Cc-scr'
<br />vation Scrv ice's rnit h~rd ro;ra;.^. ;e:hric~~, as ou;•
<br />lined in the liters;crz.'•'
<br />Co r.di lion 11 was assu'.e ~, runo:f :urve ^.u'b ers for
<br />various cover con~itions +. e:e es:irat°'-, and rair:-
<br />fall hye tog ra phs ware ce.r_ra re? `ro^ thz SCS TYpe
<br />II 2h -Hour synthetic rainfall _:ribeticn. Tie
<br />only dr pa r:ure fro^• SC'> ;achnic_Ei '•ras ;`.at e` lh^.
<br />shape of the dire ns io.^.Iess u~i: -:?ro?r==h, v.4erc
<br />the cgoa!ions propose6 cy Haag: !iS)~) -.era a,-.olicd.i
<br />The unit hyd ro_ra_A's :__. flo>' ra'P a'd tine le
<br />peak +~c re ['rose of the S".S [ria-;ular unit hydra-
<br />graph.
<br />The co :pu cat .;:dai ;hc.; gr r, aces tie run..`f
<br />h~droF¢acS= uas err; ra oad fo: re is Cveiy s,a li
<br />of [1 ce coopu ter ir, r.. "E>;cac'cd° 6~51C :~¢p;aer
<br />lan;;uag c. It is sir:`ar ro G[per rode:s that ''ave
<br />bezn re p;+rted on in [`= Iite ~a (_^r, an! ;he c.
<br />pared re sul[s have b '• qui tt :.,,a _. i).i[a1~`~pre-
<br />gram output: ere inc to=_! >:i [n so-e of the case
<br />sturiirs discussed in c'is y?e r.
<br />' F~-
<br />SC.-~. ~. a..bc r•
<br />v liar npf _-. Fri•"F ", ..
<br />
<br />r 9 I
<br />55.rr.?i SrU]JGE Sc .~, r,K'•l~
<br />TYPI~P,~_ 5~:"M,=':T CJ ti! ?~:iclL~'
<br />F~,_rv I. ''/pitdi fro `ilr o. i='i ~_n[ D2^. r_:: ", CS". 5; rci `ica:~ur.s.
<br />313
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