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'~uttleApplegate,inc. <br />Consultants for Land, Mineral and Water Development <br />PROJECT MEMORANDUM <br />,~~r,EIVED <br />FEB 181991 <br />UNL.:.UI~ ~i i.w mia~~ P Vt-OIOJy <br />96-181 <br />DATE: February 14,1997 <br />TO: John Hickman <br />FROM.• Dan Giroux, P.E~a/U~~ <br />Page 1 of 3 <br />RE: Rocky Mountain Rock Products -Deer Creek Canyon Quarry Drainage <br />John: <br />Upon review of the 1/29/97 memo from Allen Sorenson of the Division of Minerals and Geology <br />(DMG) to Gary Curtiss, we have the following comments: <br />1. Ditch Armoring Rock Size. The Division's source chart for sizing of rock armoring <br />seems to be based upon rock with a specific gravity of about 2.55, or a unit weight of <br />about 160 pounds per cubic foot. We understand the actual rock to be used ranges from <br />173 to 193 pounds per cubic foot (2.8 < S.G. < 3.1). Our computations indicate the <br />average rock size may be from 14" to 18" to account for this increased rock specific <br />gravity. The rock layer thickness may be adjusted proportionately as the avernge rock <br />size and maxirntun rock size aze customized to the unit weight. <br />2. Ditch Armoring Filter Material. The granulaz filter material will be dependent upon <br />subgrade soils. We understand the subgrades materials vary from rock to granulaz <br />materials to soils. The filter material usage, specification and depth should be customized <br />and adjusted to the actual subgrade soils for various reaches of the gulch requiring <br />armoring. <br />3. Access Road Ditch Superelevation. We have provided computations for flow <br />Superelevation for the roadside ditch. We have assumed a minimum (center of ditch) <br />curve radius of 50'. With our 8% ditch gradient, the computed cross-slope is 9.2%, <br />indicating 0.6' of additional freeboazd should be used. The detail has been revised to <br />reflect this information. The channel bottom may be banked (superelevated) to better <br />direct flows through the tighter curves. <br />4. Access Road Ditch Construction Feasibility. We understand you will be addressing <br />this issue directly with DMG staff. <br />11990 Grant Street, Suite 555 • Denver, Colorado 80233. (303) 452-661 I .Fax (303) 452-2759 <br />