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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U
PAGE :001
TIME :NAY-19-01 09:56AM
TEL NUMBERI: [phone]
NAME :Colorado Division of Minerals 8 GeoloBY
FILE NUM3ER 1T9
DATE NAY-IB 09:50AM
TO : 83037812643
DOCUMENT PAGES 006
START TIlE MAY-16 09:50AM
END TIME MAY-16 09:56AM
SENT PAGES 006
STATUS OK
FILE NUM3ER :176 *** SUCCESSFUL TX NOTICE ***
STATE OF COLORADO
DIVISION O. MINERALS ANO G[OLO[
~.V.nm.ana of Nnau,al R..ourcas Me I ~
1> 1.1 zM1. m,.n aa.. Room >l a PeablC FaY NOfY 'rert ^e o N o
Onnvee. Coloa6a faur> Te O 1 v 1. a
h.n.:l>n.tl _ ~. .... ~.. M 1 Iv a Rw r_ s
- 3 G E O L O G Y
MaY l7, 200 ] r~ i. an A t i o N
Rocky Hof7aehneidar sm La..e...
Plate Ssad 8c Gravel LLC c'^"'^`O•
P.O. HOX 180 Ems r. °"
Littleton, CO 80106 -. vlr°c~w
Mmns~s.[
oh...... v:,~.e.
li.E: RlverbaalL aad Ple Slope Armorlog Proposal. Tsehaleal Reviaioa
to SdkA Mlaa Seetlop 112 Raclamatloa Permit Application. Plaice
Valley goad sad Grave4 Flla No_ M-2000-130
Dear Mr. Hoffachnvider,
Plats Send 8L Gravel LLC has provided a [eehnleal rw ision 1TR) to Further addrsaa concerraa wish erosion
po[en[lal [hrough Lae gravel pit mining cello during a Isrge flood rent The TR Ineludea sn illustration of
locations that the ApDliemt hd determ fined [o be sensitive arena with the potential f exc a erosion. The TR
inoludee s propevsl and designs ro subiliz errain of mess potentially sensitive areas by arm rmg through the
placement of riprap. The TR nlso includes coat eaximaroa for the plscement of riprap and a description of Las
timing of riprap Installation rolntive to the sequence of ezcavation in the gravel pica. The Diviaion•e review oFthe
TR is broken out into four sec[ions iv [his memorandum as follows:
e The daecnainaxion of locations that may be aubjec[ to erosion during a Iergo flood.
e Ths specification and drawings that will govern the s ang and placement of riprap.
e The estimated cos[ to pvrohase end take delivery of riprap Last meets specification. sad to inrtall iha riprap in
accordance with designs and drawings approved by Lev Division.
e The tlmeteble £or riprap inamllatfon, in Particular the installation oT [ht/ rlVerbenk riprap.
As a rominder, the purpose of the flood convo VmiLgstion plan is tom ze the potential for exeeaslve sc ring
and v o£pi[ alopcs and of berms protecting critical sirucmros such as ages pipslvaes, grad of ofAite lanpnets
duo to aediaraentariov or roaligvmant o{the e7<irting river ellannel.
Rlprep Locmioas
In order to prey®t me s rhat may be subjett to a r during a flood vhovld be ermorod_ To
Iden[ify sross of scour, the depth end veloclry of floodwamra should be estimated end the gradation oT the soil and
ubsoll (sand and gravel) may be ertaraincd along with vegermion characterls[Ics LO demrm ins /f the erosive power
eF the flood will taut into the vegsmtion and soil. Placement eF ler8er sad heavier memrlal (riprap)- that eeaatot be
II1'kvd end moved by floodwater, will prwenL vroslon and down cutting in locations identi£ed m be prone to scour.
There aro a nutvbla• of published c mpuut:onal methods s ailnble to deaerm ins L[e sizing end gradatiora of riprap
required eo armor against erosive flows of tllTeront veloehiea.
Deprh and velooiry of fioodwaffi in ezponenrially in flood event/ of incroasingly lower probsb[liry o£
eurrence_ Ths ten-percent annual ahenco flood (Lte ao-celled ten-year flood) roau lta in a svbsmratially Ivwer
flo , depol, end vvlociry then acne-peroant annual chance Tood (L[e 100-ye.r return period wens). Designs for
armoring againrt erosion during a 100-yenr flood would moat likely fail during a much larger- but longer raum