Laserfiche WebLink
Walstrum Spur Amendment, Exhibit D—Mining Plan revised September 2021 <br /> When the Existing Quarry began operation there was no flat area for a plant and so mining was completed from <br /> bottom to top in order to open a flat floor for a plant and ancillary operations as soon as possible. If mining had <br /> been done top to bottom (i.e., top-down), setting a manufacturing facility and stockpile area would have had to <br /> wait 30 years. In this manner, diagonal "slices" were mined on the entire vertical face of the mining area <br /> precluding reclamation on any given bench until the final slice is removed. Currently the upper five benches of the <br /> Existing Quarry are at their final location and have been reclaimed over the past five years. <br /> Mining in the Spur Amendment <br /> The mining of the Spur Amendment from top to bottom is an important difference from how the Existing Quarry <br /> has been mined. By mining from top to bottom, upper benches can be reclaimed after they have been mined. <br /> Within the Spur Amendment, according to the Geotechnical Stability Exhibit, slopes can be mined as steep as <br /> 0.6HAV. This slope is measured as an overall average slope from the top to the floor of the mined area. Along <br /> each slope, benches will be created. Each slope will consist of a 30- to 100-foot high near-vertical faces <br /> separated by 20-to 40-foot wide benches, with an overall average slope that will not exceed 0.6HAV. To reduce <br /> the visual impact of the steep quarry walls, the Operator will slope the more visible slopes (above 8,000 ft) at a <br /> maximum average steepness of 1H:1V. Benches on the Spur Amendment will be shaped to wrap into the <br /> benches in the Existing Quarry as shown on Exhibit F-2. <br /> Adaptive mining methods will be used as mining progresses. Bench heights and widths will be adjusted due to <br /> geologic factors encountered during mining such as joint systems, rock types, lateral variations, and fracturing. <br /> During mining, if rock quality differs such that final geometry is affected, the Geotechnical Stability Exhibit will be <br /> updated as needed and the Division notified in the annual reports. If the structure of the rock differs from the <br /> structure presented in the geotechnical stability analysis, an updated Geotechnical Stability Exhibit will be <br /> provided. <br /> Mining in the Existing Quarry <br /> Mining methods in the Existing Quarry will continue as is currently being done. The east side will be mined until a <br /> final overall average slope that will not exceed 0.61­1:1V is achieved. This is a change from 1H:1V in the 2002 <br /> Amendment. The north side will be mined and backfilled to an overall average slope that will not exceed 2HAV, a <br /> change from 3H:1V in the 2002 Amendment. The backfilled 2HAV slope will appear more natural to outside <br /> observers viewing from the south, the original intent of the 3H:1V slope. Slope stability will be assured by mining <br /> the backside of the north dipping foliations of the north slope in a northerly direction. The west side will be mined <br /> to an overall average slope that will not exceed 1 H:1V. Mining in all three areas will begin at the highest elevation <br /> and progress down to the final quarry floor elevation. <br /> Typical mining cross sections of the east, north, and west slope areas are presented in Exhibit C-5. Factors that <br /> may impact bench widths and vertical face heights include geologic properties such as joint systems, rock types, <br /> lateral variations, and fracturing. As a result, bench widths and vertical face heights are expected to vary. <br /> 3.2 Earthmoving <br /> 6.4.4(b) earthmoving <br /> Earthmoving is performed using a combination of mobile mining equipment including, but not limited to: drills, <br /> loaders, excavators, dozers, blades, haul trucks, and water trucks. <br /> 3.3 Water Diversions and Impoundments <br /> 6.4.4(c) all water diversions and impoundments <br /> There will be no new water diversions or impoundments associated with the Spur Amendment. Water used for <br /> dust suppression and in the aggregate wash plant will continue to be pumped from Clear Creek under a water- <br /> court decree and augmentation plan. <br /> oTETRA TECH Page 4 1 9 <br />