2021-03-05_REVISION - M1977141 - Laserfiche WebLink

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Lyons Quarry 112d Reclamation Permit Operations Technical Revision Benches will be constructed 15-feet-wide at 50-foot contour intervals and will be sloped from west to east at grades no steeper than 10H:1 V. The bench width will be adjusted to achieve an overall 150- foot-high slope with a stability factor of safety greater than 1.5. All fill will be placed as follows: • Placed in horizontal lifts not to exceed 3 feet thick, based on the maximum particle size of the fill materials • Compacted to achieve greater than 90% of the maximum dry density determined in accordance with ASTM D698 • Placed in a manner that allows for a moisture content within 3% of optimum based on ASTM D698 Additional Technical Specifications for Fill are included in Section 31 23 23 of Attachment G. The average push distance for the majority of fill activities (Quarry 2) is 300 feet. The average haul distance for the catchment berm construction is 0.55 miles. Item 6.3 - Riprap for Drainage Channels and Scour Berm The toe areas of fill slopes that extend into the low-lying areas and the flood way of South St. Vrain Creek will be protected from scour by future flood events by the construction of a riprap scour berm as shown in Attachment B. The riprap gradation for the scour berm has a D50 of 28 inches and a maximum stone size of 42 inches. The riprap gradation for the drainage channels will meet Type M requirements. Riprap material sourcing and placement will need to meet the following specifications: A. Onsite, hard, durable, broken, quarried sandstone or igneous rock. Free from fractures, bedding planes, siltstone or shale layers, pronounced weathering, and earth or other adherent coatings. B. Elongation: Minimum dimension not less than 1/3 maximum dimension. C. Unconfined compressive strength: Minimum 4,000 psi in accordance with ASTM D 7012 on drilled core specimen. D. Relative Density: Minimum 2.5 in accordance with ASTM C 127 E. Gradation: The size, gradation, and weight of riprap shall conform to the requirements of the Technical Specifications Section 31 37 00 included in Attachment G. As shown in Table 3 the total volume of riprap for the Scour Berm and Drainage Channels is estimated to be 20,000 CY. This estimate could vary slightly, depending on the final alignment of the drainage channels. Riprap will be placed using CAT 740 haul trucks and the CAT 349 excavator. Item 6.4— Final Grading Final Grading of all fill slopes, benches, crest areas, and toe areas will ensure that water is not allowed to pond on or adjacent to the fill slopes. Grading will be performed to the proposed slope gradients shown in the Grading Plan (Attachment B). Final subgrades will be developed using survey equipment from Item 4.0 and a CAT D9 dozer or CAT 349 excavator. Final grades with organic material included will be developed using an excavator or tracked skid-steer to lightly spread out the material and prevent compaction. March 2021 1 17