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
FILE NUMBER 190
DATE MAY-19 09:52AM
TO 83033993680
DOCUMENT PAGES 006
START TIME MAY-19 10:05AM
END TIME MAY-19 10:09AM
SENT PAGES 006
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PAGE :001
TIME :MAY-19-O1 10:09AM
TEL NUM3ER1: [phone]
NAME :Colorado Division of Minerals & GeoloBY
STATUS ON
FILE NUMBER :190 *** SUCCESSFUL TX NOTICE ***
STATE OF COLORf~DO
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RS. Riverbaalc and Pat Slope Armeriag Propwal- Tacbaical RaWeloP
to SdkB Mloa Sectloa 112 Reclamatlon Perm/t Appllcatlop. Platte
Valley Svad sod Gravel. File No. M-2000.138
Deer Ndr. HoffacMe:der.
Platte Sma at Gravel LLC has provided n technical xvfalon (TR) m furNar address canteens wiN erosion
po,ential rhroalgla doe gravel pie m:nirag cells during a largo flood event. The TR inoludsa m 111usrration of
locations that the Appl:amS has detvrm:ned to be amsit:ve axes wiN the potentinl for exeeasive crouton. The TR
ncludsa v proposal end deaiQras so stabilize clu•teln of those potentially sens:e:ve axes by aroaoring through the
placement of ripxp. The TR also Includes coat ertimntes for the placement of riprap and a descrlptlon oT [Ile
Lim ng of riprap inrtalla[ion xlaciva m the sequence of rxcavarion In she gravel para. The Dlvislon'e ravlew of Nv
TRlia broYan out into four aectlons in Nit memormdum es Follows:
e The dv[erm lnation of locations [hat may be subject to wsion during a Isrge flood-
a The specification and drawinga Nar will govern Nv clung and plnmmvnc of riprap.
e The estlmetcd cost so puxbase and taJCn delivery of ripxp Nas meets apsclflestion, and to Install Nv riprap in
mcordance wiN designs and drawings approved by the Division.
a The timetable For rlpmp inrtallation, in paut:leuler Ne ins[allation o£Na riverbank riprap.
As s reminder, the purpose of Ne flood controVm hige[:on plm is to minimize Ne potential far excesalve scouring
nd e n of plc elopes Pod of berme promoting cMtieal savcnaxa such e: gat pipellnea. and of offsite impmte
due io sedimentation or raal:gnment of Ne exia[:ng river channel.
Rrprvp Lo,w:oar
In order to prey nc exeesslve c ac4 Net may be subject xo s r during a flood should ba errtaoxd. To
identify ax of scour, Na deptb end veloeiry of floodwnmrs should be ertimaud and Ne gnsclation of Ne toil amd
subsoil (nand and gravel) may be examined along wiN vegetation characterirtics m damrmine 1T the eroslva power
of Ne flood will cut into Ne vegemtion and toil. Placement of larger and hwv:er mamrial (riprap). d,at v t be
IiRed and moved by floodwater, will prevene erection and down cutting in locations Identified to be prone m scour.
There ax number of published computational methods alleblo to demranina xhe arz ng end gradation of riprap
xqulxd to armor egaisasc erosive flows of diffvxnt velocities.
DepN end velocity of floodwnrer inexaaea exponentially in flood svsnu of incraasfngly lower probablllry of
cumncv. Thv mn-parwnt annual chance flood (the so-called [en-year flood) xsules in a subs[miidly lower
flow, depN, and velociry Nm n one-pexens ennuvl chance flood (Ne 100-year lat,arn period event). Dea/gna for
armoring against eros[on during a t 00-ysar flood would moat liltely fail during a much larger, bus longer carom