2021-03-05_REVISION - M1977141 - Laserfiche WebLink

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Lyons Quarry �� 112d Reclamation Permit Operations Technical Revision 19% of the area includes steep slopes that would either be covered by talus riprap or remain open for nesting birds. The design for Technical Revision#2 is based on recommendations made in the Kleinfelder Summary Report of Engineering Stability Analysis for Lyons Quarry (dated February 2008). Recent discussions with BCPOS have proposed using the property for public recreation purposes as well. During the adequacy review period for Technical Revision#2, it was the request of BCPOS that the revised plan's construction approach leave as much natural slope variability to the site as possible; therefore, keeping the dacite formation exposed for geologic interpretation. Aggregate Industries and their consultant, HDR Engineering, developed a 30% conceptual design in October 2020 to present to the BCPOS to meet the following objectives: • Meet the requests of BCPOS for slope variability and preserve a section of the exposed dacite walls for biological and geological interpretation purposes, • Minimize risk to reclamation earthmoving contractors working at the base of the highwall area during backfill operations, • Minimize the amount of blasting and material handling required to backfill the northeast facing slope of the highwall, • Keep the reclamation operations within the current footprint of the disturbed mining area. A meeting was held on November 12, 2020 between BCPOS, Aggregate Industries and HDR to discuss comments and concerns with the revised plan. Many of the questions centered on the floodplain reclamation areas and were either addressed during the Technical Revision#4 development or will be addressed during construction activities. Questions about the maintenance of the reclamation components (rock bolts, catchment berms, etc.)will be addressed during the final design development. Generally, there was overall consensus that the revised plan was acceptable, and that the revised grading plan design development should continue. The revised reclamation plan's construction approach will require the following components: • Excavation and backfill of earthen material, • Construction of rockfall catchment areas at the base of the highwalls, • Scaling and stabilization of the remaining highwall slopes, • Soil conditioning and revegetation, and • Installation of stormwater drainage and erosion control infrastructure. The Site Grading Plan, Attachment B, shows the proposed cut and fill slopes and final grading. Exhibit F— Reclamation Plan Map, Attachment C, shows the planned reclamation areas and the types of reclamation proposed in Area 1, based on a slope analysis of the final grading. Section 5.1 provides more detail of the proposed Reclamation Plan and Scope of Work developed for estimating the costs for Exhibit L— Reclamation Cost, Attachment D. Unless otherwise noted, unit costs for Attachment D are based on bid tabulation results from a 2019 contractor bidding opportunity for the Lyons Quarry Reclamation. Rule 6.5-Geotechnical Stability Exhibit, Attachment E, provides the basis for the Site Grading Plan based on analysis and recommendations from the Kleinfelder Summary Report of Engineering Stability Analysis (Attachment E-1) and the Colorado Rockfall Simulation Program (CRSP) Evaluation Report(Attachment E-2). The Geotechnical Stability Exhibit limitations include a 3-year limit on the use of the report due to possible changes over time in land use, site conditions, regulations, or other factors. As stated in Attachment F of Technical Revision March 2021 1 5