10-17-1994 Planning Packet - Laserfiche WebLink

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Mr. Dak Gusufson October 11, 1994 Page 3 on the fine grained shore nulerials pnor to placing the riprap. This filter layer is intended to reduce erosion of the fine grained shore soils. We recornmeod a woven filter fabnc intended for this purpose and meeting the specifications of Nicolon 70^06 fabric. For this type of wall system. se%-eral condinons must be evaluated to determine the wall system geometry required so adequate lateral suppon is attained. Those conditions and minimum factors of safety we have considered are as follows; • Bearing Capacity Failure - Safety Factor ■ 2.0 • Base Sliding - Safety Factor *1.5 • Wall Overtunung - Safety Factor * 2.0 • Overall Slope Failure - Safety Factor * 1.5 • Geogrid Overstress - Safety Factor » 1.2 • Geogrid Pullout - Safety Factor = 1.5 Your proposed wall system has three general geometrical cross-sections. • Walls separated by relatively large distance with a slope upward away from the lower wall of 2.5:1 to 3:1 (horizontal:vertical). • Up to four terraced walls at spacings of as little as about 6' and an overall rise in elevation away from the shoreline of about 2.5:1 (horizontal:vertical), with backfill between individual walls relatively level. • Two-tiered wall system with relatively level grades between and above the walls. Adequate bearing capacity of the wall system will require replacement of all organic or soft soils within the area of the walls. This includes all soil materials which shifted as a result of the slope failure several years ago. For access to the planned construction atea, it appears that the e.\isting trees and shrubs along the shoreline will have to be removed. If they are, all roots should be grubbed and cleared from the area. We recommend observation of the excavation areas by an experienced soils engineer or technician prior to fill placement. Supporting earth materials beneath the wall system must be either firm, natural soil or compacted fill. The fill material should preferably be fine gravti with a maximum largest