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6-inch --- 35-50 3-inch 2-10 ---- 2-inch --- 2-10 Minimum riprap thickness shall be 1.75 times the Dso rock size. 5.7. AGGREGATE BASE COURSE 5.7.1. Aggregate Base Course material shall consist of processed soils from Area D that meet the requirements for the Colorado Department of Highways Class 5 Aggregate Base Course specification. Aggregate Base Course material shall have a minimum California Bearing Ratio of 40%. 5.8. GEOSYNTHETIC DRAINAGE FABRICS 5.8.1. Geotextile fabrics used as an underlayment for riprap and for drainage control shall be non-woven style synthetic fabric with physical properties equivalent to Mirifi 180N. 5.9. STRUCTURAL SOIL REINFORCEMENT-GEOGRID 5.9.1. The geogrid shall be Tensar Structural Geogrid BX1200 or equivalent. 5.9.2. The geogrid shall be integrally formed and deployed as a single layer having the following characteristics. Pro ert Tes[ Method Limitin Value Aperture Stability Modulus at 20 cm-k Kinney - Ol 6.5 cm-kpJdeg Rib Sha a Observation Rec[an ular or S uare Rib Thickness Cali ered 0.05 in. A enure Size LD. Cali ered 0.9 to 1.5 in. ]unction Efficienc GRI-GG2-87 93 ercent Flexural Ri idit ASTM D1388-96 750,000 m -cm Minimum True Initial MD - 27,420 Ib/ft Modulus in Use ASTM D6637-O1 CMD - 44,550 Ib/ft 6. CLEARING AND STRIPPING 6.1. All borrow areas, areas that are to receive fill, and areas that are to be excavated for structures, culverts, or ditches shall be stripped of all sod, brush, roots, other vegetation and soft soils, including top and organic soils, to a sufficient depth to remove organic soils and to expose sub-soils appropriate for support of new fills, as determined by the Engineer. 6.2. Sod and vegetable matter shall be separated from the topsoil as much as practical and stockpiled for reuse at locations designated by the Engineer. 6.3. The depth of removal shall be a minimum of 6 inches in areas to receive select fill and the minimum amount that can be practically salvaged without unnecessary dilution by non-organic earth materials in other areas. Additional stripping may be required when, in the opinion of the Engineer, suitable materials have not been exposed. 6.4. All areas that are to receive common fill shall be stripped of roots, trees, and other bulk vegetative matter and debris. All top and organic soils of common fill areas shall be selectively stripped and stockpiled for reuse. 6.5. All suitable stripped materials shall be stockpiled at a location designated by the Engineer for use in reclamation of disturbed areas. Stripped materials of different types, such as roots, dead trees, or brush shall be SPECIFICATION A EARTHWORK PAGE 4