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MEMORANDUM <br />have a disadvantageous orientation and location, then there could be a large scale slope instability. <br />However, field observations by Lyman Henn and by J A Cesare did not reveal any such joints. Based <br />on current information there is no reason to believe that there would be a high risk for such events. <br />As verification of these slope stability evaluations, an Observational Approach will be used to develop <br />the quarry. Using this approach, a small area of the mine in the first phase and away from the limit of <br />mining will be excavated first and used to observe actual ground conditions and rock slope behavior. <br />Providing that observed conditions are consistent with the basis of these slope stability evaluations and <br />that the rock slopes do not show unexpected behavior, the mine will be developed to the maximum <br />extents as proposed in the mine plan. Additionally, with the upper portion of the mine at a more gentle <br />slope inclination than the lower portion of the mine, a similar reassessment of the rock slope stability <br />can be made and appropriate changes to the rock slopes made when the mine is extended below <br />elevation 5800. <br />Soil Backfill Slopes <br />Soil will be placed on benches as part of mine reclamation. This soil is expected to be overburden <br />removed from above mineable rock, weathered rock, and unsaleable rock and fines as a byproduct rock <br />processing. It is further expected that this soil would receive a low to moderate degree of compaction, <br />except for weathered and waste rock containing large particles which is impractical to compact. These <br />soils are all granular with angular to sub-angular particles and no more than approximately 25 percent <br />fines (material finer than the number 200 sieve). <br />Soil slope stability calculations are based on a purely frictional analysis neglecting cohesion, which is a <br />conservative assumption. Soil friction angles were estimated from correlations based on soil type and <br />density. A safety factor of 1.1 was chosen by Lyman Henn to be the design criteria. Based on these <br />analyses, it calculated that fill derived from overburden and unsaleable material cold be placed on slopes <br />of 1.75H to 1V or flatter, and that weathered rock could be placed on slopes of 1.5H to 1V or flatter. <br />With a high level of compaction and with laboratory testing to verify the soil strength, it is expected that <br />any of these materials could be meet the design safety factor on a slope with an inclination of 1.511 to <br />1V. <br />\\Server0l\common\PROJECTS\106052-000 Parkdale Mine Plan\R. Records and Correspondence\R.08 Design Calculations\Stability Memo.doc