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CALCULATION OF FACTOR OF SAFETY FOR SLOPES,SCHMIDT SITE M2011-014 <br /> Purpose:In accordance with MLRB Policy 30.0(Factors of Safety for Slope Stability Policy),this report <br /> determines the factors of safety for the slopes for the Schmidt Site, including the relocated entry road <br /> and other filled/cut slopes,with and without toe walls/facings. <br /> Scope:This applies to the northern portion of the Site(approximately 250 feet from the north (street- <br /> facing) property line and north of the power line crossing the Site east to west). <br /> Summary:The soil conditions and materials available,when properly selected and placed,ensure that <br /> the 2:1 or flatter slopes and the low walls(6-ft rock or 5-ft tires/tire bales) have an adequate factor of <br /> safety(greater than 1.7)and therefore have a long-term life and meet state reclamation standards. <br /> Description of proposed slopes and walls: <br /> The slopes will generally be 2H:1V or flatter. The highest/longest is the eastern slope.This will match to <br /> the existing natural grade approximately 10 feet from the eastern permit boundary with a maximum <br /> height of 20 feet, and approximately 5 feet from the western permit boundary with a maximum height <br /> of 15 feet,and runs approximately 75 feet(of which only about 50 is at the maximum height.About fifty <br /> feet length of this slope will be backfilled by filling the existing road cut,which had a slope of <br /> approximately 10 feet maximum height on the west side of the 15 feet wide road cut. <br /> The new road alignment will be a maximum of 25 feet wide and have cut slopes to both east and west <br /> (2:1),for approximately 50 feet length (100 feet total of both sides).These slopes will be approximately <br /> 8 to 10 feet high, and therefore 16 to 20 or so feet wide.The top of the west cut slope will be 10-15 feet <br /> from the west parcel boundary/property line.As much as possible, existing large vegetation (trees and <br /> bushes)will be kept for both soil retention and esthetics. <br /> Existing and relocated drylaid stone walls may face some portions on the roadway and interior faces, <br /> with a maximum height of six feet to eight feet.The boulders used for these will be as large as six-feet <br /> (maximum dimension)down to approximately 1 foot maximum dimension,and will generally be laid <br /> against cut or placed/compacted soil at a 75-80 degree slope from horizonal.Tire walls may be used on <br /> the roadway and interior faces, at the toes of the slopes,for a maximum of 5 feet height(two tire bales). <br /> Other slopes,a mix of cut and backfill,will be 2:1 or flatter around the excavations(pit floor areas). <br /> Although I refer to these as walls, much of the stone is more a facing than a wall. <br /> There are no significant manmade structures within 200 feet of the slopes or the exterior permit <br /> boundaries,except a fence jointly owned by the Schmidts and the neighbor to the east,Susan Moak. <br /> (Refer to drawings in technical revision and original permit application. In accordance with MLRB Policy <br /> 30.4,the fence is a "Non-Critical Structure" and therefore the applicable Factor of Safety(FS) is 1.3. <br /> The type of slopes proposed are hybrid,that is,a gravity retaining wall using some earth-reinforcement, <br /> and an exterior facing. This provides a greater FS and also allows for variations in materials both of the <br /> wall itself(dry-laid stone,tires/tire bales)and the backfill.The slopes, up to 70 feet in length,will be <br /> constructed using on-site soils and stone.Some areas will have the stone walls or use 5 x 5 x 2.5 foot tire <br /> bales (each weighing approximately 1,000 pounds(1 kip),and with a footprint of 25 square feet)at the <br /> toe,with one or two layers of bales. <br /> Method of Analysis: The primary method of analysis is US Army Corps of Engineers Method found in <br /> Chapters 3 (Forces and Walls)and 4(Structure Stability), EM-1110-2-2502.An adequate assessment of <br /> stability must include a rational assessment of loads and must account for the basic structural behavior, <br /> the mechanism of transmitting compressive and shearing loads to the foundation,the reaction of the <br /> foundation to such loads,and the secondary effects of the foundation behavior on the structure. Limit- <br /> Equilibrium Analysis is used with the required Factor of Safety to evaluate failure and determine if the <br /> wall is safe from bearing failure and overturning. <br /> Stability Analysis M2011-014 Schmidt Site Page 1 of 3 <br />