PERMFILE60699

• Permit No: M2000158
• IBM Index Class Name: Permit File
• Doc Date: 5/18/2001
• Doc Name: Riverbank Faxes
• From: DMG
• To: PLATTE SAND GRAVEL LLC
• Media Type: D
• Archive: No

MEMORY TRANSMISSION REPORT
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PAGE :001
TIME :MAY-16-O1 10:4TAM
TEL NUMBERI: [phone]
NAME :Colorado Division of Minerals [ CeoloeY
FILE NUMBER 199
DATE MAY-19 09:59AM
TO $19703561111
DOCUMENT PAGES 006
START TfME MAY-16 10:43AM
END TIME MAY-16 10:d7AM
SENT PAGES 006
STATUS ON
FILE NUMBER :196 *s* SUCCESSFUL TX NOTICE ***
STATE OF COLORe°~O
DIVISION OP MIN EQALS ANO GEOLtOGY __, _ _
Oaparnnrn[ o! Na[ural Resourwt -
1 ] 1) 91,~rman 5[.. Room ~l ]
Onnver, Colorb[!o 90]03
Aone: 1]9]1 966-)ib>
fA.x: (]O)) 9]3-9109
May 17, 2001
Rocky Hoff chnaidar
Plnrte Sand !~ Gravel LLC
P.O. 80X 1 BO
Lialeton, CO 60106
Peat-IC Fan N°t¢ 7e"rl °° a ~
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R'$: Iilverbavlt avd Plt 9bpe Armwrieg Proposal, Teehvfaal lisylalon
to Sdo<8 Mlva Saeitov 112 ReGamaHOV Passnlt Appgeatioa, Pla[b
Valtsy Sand avd Gravel, Ffla No. M-2000-13g
Oew 1V[r. Hotfcchneidw,
Plnrte Sand $ Gravel LLC has provided n technical rwla:on CCA) m fLlther address conc¢ma wilt erosion
potential througfi the gravel pie mining veils during o large flood teens. The TR includes an Illuexration of
locations that the Applicant hu dcxermiaed to bs s sixivc me with the potential for excessive erosion. The TR
ncludss a proposal end designs m arabiliza veru:n o£thesa petantlnlly a :ve weu by ormoring through 4[s
placement of rlprap. The TR also includes coax cac:matss for the plvicemenr of ripmp and a description of the
timing of ripmp insmllarion rolexlya to she sequsnee of azeavatlon In rho gravel pie. The Division's revises of the
TR is broken out tam Four sections in this memorandum es Follows:
The damrmina[lon of lovatlons that may b¢ subjevt toe n during a Iwge flood.
• The epceiflcaslon and drawings rhrt will govern xha siz pg[ana placem¢nx of rlprap.
The estimated vort m purvhass and take delivery of ripmp that meeo speclTicaLOn, and to Install the rlprap In
cordmce wlrh designs and drawings approved by xha Division.
• Tha dmemble for ripmp installaeion. in pwrdculw the insullaxion oEthe riverbank ripmp.
Aa n reminder, the purpose of ehv flood convol/m1[lgatloa plan Is ra minimize the potential for exarssive scouring
and erosion of pit slopes and of berms protecxing critical atnrcmrcs such u gam pipelines, sad oT Offsits impa¢[e
due m svdimevmx{oa or realignment of she azisting river channel.
Riprgp LornHnvs
In order to prevent eacvsasive w nrces xhat may ba aubjecr m scour dur'utg v flood should bs armored- To
identify areas of scour, the depth end vslociry of floodwaters should be estimated and the gradation of the voil and
subsoil (sand end gravel) may bs examined along with ycgemtion chsrwctar:acies xo darerm ins if the erosive power
of the flood will cut inm rite vagautlon and soil. Placement oT largw and heeviw maur:al (ripmp), skier owrmot ba
lifted and mwsd by floodwam, will present erosion end down Dotting in locations idenrifled m be prone to scour.
Thos era mbar oT publ/ahsd ¢ mputaxionnl m¢thoda a wilnbla m dctcmiine she sizing and gradation of rlprap
required to armor against wosive Slows of different velooitiea.
L)eyth and valoclry of Floodwamr increases exponential ly in Tiood svents of incrauingly lower probability of
reno¢. The ten-perc nt ann al shears flood (xha so-called ten-year flood) rcaulra in a substantially lower
ilnw'depth. and velocity than none-peroent art[[ual chance fleod (the 100-yew roturo period avant)- Designs for
armoring againa[ erosion during a 100-yew flood would mort likely fail during s much Iwger, but longer return