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• i <br />vibration records are maintained at the site offices. Recent blasting technique improvements include pre-split <br />Perimeter control blasting techniques that focus blast energy within the blasted rock mass and minimize blast <br />energy propagation into the rock mass outside the final cut line. This technique is routinely being applied at <br />final cut blasts to improve rock quality and slope stability of final highwalls and benches. <br />:secondarily, the new blasting technique minimizes blast-induced fracturing that would increase bedrock <br />permeability near the proposed reservoirs. This has the beneficial effect of reducing potential seepage losses <br />from the reservoirs above the ground water table and of reducing potential inflow of ground water during <br />periods of reservoir drawdown. This is also being done to reduce the potential sealing costs associated with <br />reservoir construction that might be required to minimize seepage losses or inflows. <br />13.04 North Quarry Engineered Fill Slope <br />The newly proposed North Quarry engineered fill slope is included in the mine plan primarily as a means of <br />improving the visual appearance of the existing exposed highwalls in the southwest comer of the North <br />Quarry. Previous plans were to re-mine this area at a flatter slope angle (1.5:1, H:V), then improve visual <br />aesthetics by completely backfilling the flatter bench configuration. Now it is proposed to cover the subject <br />area with a large engineered fill extending well out from t}te toe of the existing highwalls. <br />Presently, studies are being undertaken to determine the design of this slope. These studies include labomtory <br />testing of proposed fill materials. Upon completion of laboratory testing, design will address slope inclination, <br />limits, materials, construction requirements, foundation requirements, and drainage. Because the necessary <br />design data is not presently available, this Mine Plan Amendment presents a general outline of fill slope <br />features along with design criteria for the slope, rather than a set design. CAMAS proposes to meet a <br />performance factor in the form of a target safety factor so that this permit Amendment No. 5 may be submitted <br />before final design is complete. <br />The fill is essentially an embankment fill slope constructed against a stable rock slope. It is expected to have <br />an inclination of approximately 2 horizontal to 1 vertical (2: L), but could vary from as steep as 1.5:1 to as <br />shallow as 2.25:1. A buffer zone approximately 40 ft wide will be provided around the perimeter of [he slope <br />toe and flanks. This buffer is for slope access and to prevent vertical quarry highwalls from undercutting the <br />fill slope from below. The fill will consist primarily of granular soils obtained from within the quarry. These <br />granular soils will likely be primarily structural fill, but may also include granite sand, unsaleable and non- <br />topsoil overburden and poor quality rock, and, to a limited extent, fines resulting from wet aggregate <br />processing locally known as "jade-air fines". Pending results of the laboratory testing and detailed design, the <br />jade air fines may be solidified by belt-pressing, or strengthened with cement and/or fly ash to improve <br />strength. <br />G?PROIERS~IO:0Q~O0T X'MMFNOOS.TM XII - 2 <br />