2001-05-22_REVISION - M2000158 (3)

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iwVlfl OwMLNT. Iwe. r140t M.r aa, suu 1 Attached aye typical cross sections that will be used to design the bank armoring. They are from the Division of Minerals and Geol- ogy's Inetream guidance document (L+igure D-5, Flyure D-7, end D-0}. eroposod erawsing plan Pickett fingincering used a D~a equal to 24 inches and the Divi- elon suggested the minimum thickness should be D„ x 2.o ror the pit banks ens Duo a 1,75 to Duo x 3.0 on the river banks. Theaw guidelines will be followed. If a ehenge is necessary, revisions will be submit- ted to the Division ror review end approval. Armoring will be doubled on each end of a reach whetl~sr In a lake or on the river, if it ends on a natural bank. Pit 6lopaa The pit elope armoring will be placed on elopes no steeper than 2.SA to lv ae shown on the guidelines. The thickness will be calcu- lated by using D~„ x 2.0 to nPtPrmine the thickness. The applicant propoooa using concrete rubble asp riprap material. This material Is readily available to Dlatte Sand t ~rave.l and has been proven e!!eC- tivo on other minas throughout coloradn. The concrete rubble 1s anyular~ durable, and non-slaking in nature, but phyaicAl testing end documentation showing that it meets the requirements and thw gradation nNC~i2lcation will be conducted on the material prior to now nn each 9o0-foot eeation. Physical testing will include a slake teat and an abrasion test to ba sure the rubble is suitah.le for riprap. Any unsuitable a~aterlal will be used as fill as explained in the permit application. The records cl Che teat results will bo kcpt in the corporate dEi'ices for review. Prior to placing the riprap tl~m applicant wi.t.1 conduct aL• lcaot one gradation teat !or each 700 linear Eeet of riprap inetniletinn ro determine 1Y the itt situ material ie suitable for the bedding. This will be done to demonstrate and document dial l'he filter bedding ie compatible with the riprap. This bedding will be a filter blanket of gravel, or sand and gravel that Will prevent Boil movement: i.uto oz through the riprap. It is possible that the in eitn mater.l.als will create auitabls bedding, particularly on the pit elopes sihre pit run sand and gravel usually makes a good filter blanket. The Armor..ing will cover a band from the existing ground surface to an elevation 3 feet below Cha river invert on any given section and will he keyed itt or doubled per the design apscifieatione providwd i.n the Division's guidance document. On the code of thv armored pit banks thr riaph.h hOd HdBS:C TQIOZ ZZ 'FQIJ 6 ~~ C2h COC~ '^FI 3hL7Hd 'JF71 '1N~LlFi7?J [(1F1~ ~:~n id