2016-07-01_REVISION - M1977141 - Laserfiche WebLink

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Lyons Quarry �` ` 112d Reclamation Permit Operations Technical Revision ".�/7T1, The flattest measured slopes were in areas mapped as landslides. Existing natural slopes in the dacite are nearly vertical where the dacite is exposed along the north side of South St. Vrain Creek. Where the dacite outcrops in the drainage along the west side of the site, the existing natural slopes range from 0.3H:1.OV to 2.21-1:1.OV. This large range in the natural slope was measured along west facing slopes over a span of approximately 300 feet. Vegetation is generally absent in the leveled and mined areas. Vegetation over the remainder of the site is described by previous investigators as grasses, forbs, and shrubs/brush with various cottonwoods, willows, Virginia creeper and golden current found along the drainages. Surface water is present along the north edge of the site, in South St. Vrain Creek. Groundwater is present, ponded in low areas and observed as wet areas along the base of the highwall. Groundwater is also anticipated perched above siltstone and shale layers in the Fountain Formation. 3 Exhibit E — Reclamation Plan The anticipated post mining use for the site is to provide as cattle range and pasture land in the production, stockpile, and pit floor areas. The following paragraphs provide a summary of the proposed revised Reclamation Plan for Lyons Quarry. The Site Grading Plan, Attachment B, shows the proposed cut and fill slopes for reclamation. Exhibit F— Reclamation Plan Map, Attachment C, shows the planned reclamation areas based on a slope analysis of the final site grading. Section 5.1 provides more detail of the proposed Reclamation Scope of Work developed for estimating the costs for Exhibit L— Reclamation Cost, Attachment D. As a first step toward final reclamation, prior to mobilization, an updated topographical survey of the site will be conducted to establish the 100 and 500-year floodplains as well as site perimeters and slope staking. An inventory will be taken of existing structures, utilities, and remaining equipment to be demobilized and/or disposed of. A project safety plan will be developed to consistent with MSHA requirements prior to initiation of field activities. Prior to any earthwork, utility locates will be conducted. Due to the flooding in 2013, site conditions have changed since the mining activities ceased in the mid-2000s. Erosion control Best Management Practices (BMPs), will be implemented to restrict sediment transport from the site to the South St. Vrain waterway and control dust generated by construction activities. Appropriate measures shall be taken to ensure areas outside of the affected land are protected and the handling of refuse or hazardous materials are disposed of properly. Once the site controls are installed, the grading plan will be implemented. All reclamation slopes are to be cut to 1.5H:1 V slopes in the overburden sedimentary rock using drill and blast methods and filled to 2H:1V slopes in the quarry areas in accordance with the stable cut and fill slopes described in the Rule 6.5 Geotechnical Stability Report, Attachment E. All backfill will be moistened, placed and compacted to achieve adequate density for stability. The revised Site Grading Plan is shown in Attachment B. Fill shall be placed in horizontal lifts not to exceed 2-feet thick. Compaction requirements will depend on the lift thickness and the equipment used, but adequate compaction should be achievable by tracking with a dozer or with the routing of construction equipment traffic, provided material characteristics, moisture content and lift thickness are appropriate. Final grading of all fill slopes, benches, crest areas, and toe areas should ensure that water is not allowed to pond on or adjacent June 2016 1 3