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<br />MEMORY TRANSMISSION REPORT <br /> <br />PAGE :001 <br />TIME :MAY-19-01 10:25AM <br />TEL NUA8ER1: +13039fi63567 <br />NAME :Colorado Division of Minerals i CealoeY <br />FILE NUMBER 193 <br />DATE MAY-19 09:55AM <br />TO $3036201379 <br />DOCUMENT PAGES 006 <br />START TIME MAY-19 10:21AM <br />END TIME MAY-19 10:25AM <br />SENT PAGES 006 <br />STATUS OK <br />FILE NUMIOER :183 *** SUCCESSFUL TX NOTICE *** <br />STATE OF COLORADO <br />DIVISION OF MINE¢ALS ANO GEOLO~`-'-" '-- -""'- <br />I1aParnnan. sI Nawr~l Ro.ou/ce. <br />a ahvman St.. Room T] <br />Ornva/. Colo/ado BOa03 <br />VAYna_ 19031 846-'l]af <br />anal sea-elos <br />May 1 7, 2001 <br />Rocky HoHichnaider <br />Platte Sand dL Gravel LZC <br />P.O. HOX 1 BO <br />Lixtitton, CO g01015 <br />Poab1C Faf[ NotB "18'11 as O $~a <br />xo Fom <br />Oa Y.. Ce. <br />en. Prena <br />17<T: Raverbavlt sad Pit Slope ArmotYag Proposal, Technical licvLlov <br />to 94413 Mlne 8ectloa 112 lieclvma[iov Perml[ Appllusiov. Plana <br />VWlay Saad avd Gravel, Fite No. M-2000-13g <br />Dear Mr. Hoffaohneider, <br />.~ <br />M l N 6 R A L 5 <br />G E O L O G Y <br />w pG N~Ma <br />Gin.[a.-... <br />e..,a e. <br />.~n.a <br />own~on o::::e. <br />Pin[xe Sand Bc Gravel LLC hen providmd a csehnlaal revision (TR) to Arrdler addrose conesrns wit:r erosion <br />potenr:nl thro[rgh the gravel plc mining cells during a largo flood w nt. The TR includes sn :Iiustraslon of <br />lout[ons that she Applicant lens demrmined xo be srns:t:ve areas wirh the pomntinl { r «oevaiva erosion. The TR <br />Includes a proposal and dssigas to smbllize cesta:n of these pommially aensi[:v arem by aro ng through the <br />placemens eF rlprap. The TA also :aelvdes cost ertimams Tor xhe placement of riprap and a daaerip[ion of the <br />liming of riprnp incrallntion relative to xhe sequence of excavation in the gravel pits. The Division's rwlaw of xhe <br />TR .s broken out into four sections in this memorandum as follows= <br />a The demrmina[ion of locations that may be subjaee to aroslen during v large flood. <br />The apeci£cadon and drawings shax w111 govern xhe sizing and placcmenx of rlprcp. <br />s The ertimamd eovK so purohms and xdce delivery of riprap shat meem apmiflcsxlan, and m Install the riprap in <br />eco[dvnce with designs and drawings approved by the Division. <br />a The timetable { r riprap :narNlation, in particular the installnsion of the riverbank riprap. <br />Asa minder, the purpose of the hood eonvoLml[Igarlon plan is w m mfze the pommlal for ezcesalve scouring <br />end erosion of pis slopes and of bsrma promcting critical sauetures such m gm pipelines, and of off im impaees <br />due to sedimentation or rcalignmens of she aatissing river channel. <br />Rlyrop Lpcnrlnras <br />[n order eo prwwt exesas:ve aro areas max may be aubjett to scour during a flood should be ¢rmora-.d. To <br />identify arom of eoour, the depth dad veloeiry effloodwamis should be eat:mstad and the gradation of then wii and <br />abaoll (nand and gravel) may ba examined along with vegemtion eharecteristias m damrmine If the erosive power <br />of the flood will cut Into the vegemciott and soil. Plscamans of larder and hesvlsr mamrlal (riprap), thns cannot ba <br />I/Red and moved by floodwnter, will prevent erosion end down euRing In locations idmtif'ied m be prone re scour. <br />Thar umber eP published wmpvtatienal rncrlreds a ailabls ro determ ins the sizing end gradation of riprap <br />required se armor agalnrt erosive flows of dill rent velocities. <br />Dspxh and velocity of floodwater Innremes oxpoventinlly In flood wenxa of incremingly lower probnbf llry of <br />T]ra n-percent a a1 abet. a tlnod Cxha ailed tan-Year Heed) ra alts ubawtlallY le <br />flow, depth, end velocity than none-parcens annual ohaaea flood (she 100-year return period a cox). Designs £or <br />armoring ngainsx erosion during a lOo-yeer flood would moo[ likely Teil dating a much larger, but longer return <br />