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11: Ub~ H~ 11 '.UU QJUJSbGULUU tlHU Uk.A1bH !V iUiC <br />ILS UUO <br />(:) T:se gabion baskets should be txansitioned az keyed <br />into tae bank and secuzeiy tied to eac!~ et~er. <br />• 7. D&Op ST3UC'"L~. ,1 drop 9tructute is a ~eup oc roaka, <br />beulder3 ono/or legs placed Sn a stream to acs as i low level dam. <br />?'_acsment of a drop structuze vii: raise the st~eamb~d elevation, <br />decrease trio stream gradient immediately upstream, dissipate <br />stzeam enszgy, decrease current velocity and reduces st~eambank <br />ezcsian while premotiag stxeambed stability. ?lacement o: 3zoo <br />strueturas is authorized provided: <br />la) Dsop stxuctuzea shall be eonstractsd se that the <br />maximum Height above the existing a:raambed shall not extend two <br />feet. The majority of drop at:uctuzas employed in the 3tnte of <br />Colorado would not need to excaad this limitation to promata <br />s.tzeaabank and streambed stability; <br />(b) Materials acceptable Eor drop structure <br />eonat-ua:ion ineluGa large boulders, laze angular stone az =eek- <br />°_illad gabion hasketa and logs in cambiratian with any o: the <br />preceding i.e. large boulders, large angular stone or rock-f1'_led <br />gabion baskets; <br />(c; Matasial size shall be large enough to •rithatand <br />•xpeetnd hi fit f'_or velocities and aasociate3 turbulenC~; <br />Id) Drop struc:uzns shall be COn7truC=ed Straight <br />across a stream channel perpendicular to the currant or morn <br />preiazably, in a "V" shags with thq point o: the "V" dizected <br />upstream. This "v» shooed eonfignratian wi:l direct overtopping <br />• flows to the middle et the rives and not against a37aCent <br />stzeambanka; <br />(e) ]ill drop stzuct uea shall b• tied or keyed into the <br />e:cistinq banks and pretoeted by large rock anchored 9evezal feet <br />into the hoax. Protecting the l3anka of ttte structure is c=itieal <br />to prevent extensive daauge from high !lows; <br />(~) Construction agnipment ahauld aCCeals Lhe 9tredm <br />only at a location immediately upstream of the proposed stzucture; <br />(g) Constzuction or placement of rock far a drop <br />Structure Shall start at both banks and pzocsed tovrazd th0 middle <br />of the stream. !- baekho• or front-end loader, pzeferably wish an <br />opposing "thumb" en the hucYet to manipulate the rocky, has been <br />found most useful censtruetinq drop structures; and <br />(h) Due the varied widths o! streams wherein a drop <br />structure may be woeful Ln stabilizing stxeambaaka and atzeacnueCs, <br />a specific limitation on the volume or material discharged is not <br />being employed. However, the drop stsuesure moat nos exceed 2 <br />feet in height above the pre-structure stream bottom elevation. <br />1. TTIS Jetties are structures which ors placed along <br />a bankline to direct the flow away fzem an eroding bank. Jetties <br />~. ~ <br />• <br />