2020-06-16_PERMIT FILE - M2020007 (7)

Home Browse Search

Environment, Inc. Page 2 Adequacy Response#2 June 11, 2020 M-2020-007 required. A cost to remove their concrete supports is included in the Reclamation Cost Estimate as concrete removal. The Mining Plan has been revised to explain this process and updated to match the mining plan revisions based on the proposed bonding discussed later in this response. Pit side and lateral berm widths/armoring — please see following comments under Exhibit E and address accordingly. See response for Exhibit E. EXHIBIT E - Reclamation Plan (Rule 6.4.5): The proposed mining and reclamation plan submitted states that a minimum of 150' will be maintained between the base of the existing berms/levee and the mining extent (top of pit), however no pit wall armoring or flood control structures have been included in the mining or reclamation plans. To insure that final reclamation configurations meet requirements for long-term stability, DRMS defaults to the recommendations provided within the UDFCD Guidance for Gravel Mining and Water Storage Activities Within or Adjacent to 100-Year Floodplains for sites adjacent to the South Platte River and its major tributaries. According to UDFCD guidance Table 2.1 River top Berm Width (page 27); even if DRMS assumed that the existing riprap on the bank of the South Platte met the specifications for riverbank protection, the minimum top width of the riverbank berm with no pit-side protection would be 250 feet. If both riverbank and pitside banks are protected according to the provided guidelines, the guidance states that a minimum rivertop berm width of 150 feet is acceptable. The armoring done along the river bank and the construction of a secondary protection berm done by landowners in the past is adequate for protecting the riverside bank from flooding. This is evident and proven as both the armoring and berm have been in place for many years and resisted both the 2013 flood event and the 2015 high water periods most recently. In response to the Division's reclamation recommendations noted above, L.G. Everist's in-house engineers prepared an analysis of the river along the west sides of Phases 1 and 2 and determined that the most advantageous way to proceed was to armor the pit side of the bank of both Phases because they lie in between the 250 foot and 150 foot setback as proposed in the Mining Plan. In Phase 1 this amounts to approximately 3195 linear feet and in Phase 2 approximately 1983 liner feet. L.G. Everist will commit to armoring the west banks of Phase 1 and the Phase 2 as shown on the Reclamation Plan Maps and as described in the Bank Armoring Plan that is attached. This will be done from the surface of the ground to a point 5 feet below the thalweg of the South Platte River with a face slope of 3h to 1v using concrete rubble with all exposed rebar removed, see Figure 1 in the Bank Armoring