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Hazeltine Mine Spilway;Adams County <br /> ELEVATION CHANGE <br /> The original designed spillway had a capacity of 7,100 cubic feet per second(cfs)with one foot of <br /> free board. The new design calls for the spillway crest to be raised 1 foot(from 5,039.8 to 5,040.8 <br /> feet on the riverside),but will have the same cross sectional area. Thus the capacity remains the <br /> same but there is no freeboard. <br /> CONCRETE APRON <br /> The concrete apron on the spillway crest will be 1 foot in thickness and reinforced with No.4 rebar <br /> 18-inches on center. The reinforcement will be structurally tied into the vertical, concrete cutoff wall <br /> and ribbed center bulb PVC water stop will span cold joint between the cutoff wall and the apron. <br /> The concrete apron was designed to resist uplift from flows over the spillway crest. The analysis was <br /> conducted using information published in the USBR publications Uplift and Crack Flow Resulting <br /> from High Velocity Discharges Over Open Offset Joints(DSO-07-07) and Design Standard 14 <br /> Appurtenant Structures for Dams(Spillways and Outlet Works). An uplift force may occur on a <br /> concrete slab when there is an offset joint. This force is counteracted by the weight of concrete and <br /> weight of water at the joint. Using the methodology in the publication,the uplift force and resisting <br /> forces were calculated for the concrete slab. The maximum flow velocity was estimated to be <br /> approximately 20 feet per second at a flow depth of 2 feet. The calculations show that a 12 inch <br /> thick slab has a factor of safety of 1.1 for resistance to uplift forces. <br /> Uplift calculations are provided in Attachment 2 of this memo. <br /> Attachment 1 Design Memo January 21, 2008 and Riprap Sizing Letter April 7, 2008 <br /> Attachment 2 Additional Calculations <br /> (Copies of the April 23,2008 UDFCD letter,June 6,2008 Adams County Amended Flood Plain Use Permit and January 20,2016 <br /> email communications between Gary Linden of Tetra Tech and Adams County Senior Engineer Gary Labrie regarding an extensior <br /> the Floodplain Use Permit for the Hazeltine Mine spillway together with the"No Rise Certification"referenced in that e-mail have be <br /> inserted in Attachment 1 by Connie Davis,Aggregate Industries.) <br /> P:�23514133-23514-I5002`Docs Spillwav\Hazeltine Spillway Des Memo 2.doc <br /> 2 <br />