03-21-1988 Planning Packet - Laserfiche WebLink

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:al drop for every te for stabilizing a continuous 2*1 tployed to provide two categories: ty so that steeper tendency to fail. as retaining walls, urden soil so that >yed. of the soil to move red by staff is as orm slope with no out a 1.4:1 slope better than what be disturbed soil rhis method would te, but would be f vegetation. The ould be relatively 5 prime short term be laid bare for a Note that use of bales, seed mesh, actual short-term 4%••Vi va‘:VZoning Pile 11221 March I, 1988 Page 4 of I B. This method proposes to excavate the bank slope area, build a cribbed interior stabilisation structure and then refill the bank to the original (1.4:1) grade. The interior cribbing bec<»es invisible because it is covered with sol), hence allows the steeper slope to be naintained while making it much more stable. In order to construct the cribbing, a large askount of soil must be excavated and stock piled on the site, but this is merely a short-term concern. There xrould be slightly greater area of bare soil during the re-vegetation period as compared to Option A. This auithod is relatively expensive due to the materials and excavation involved, but would allow for a relatively stable restoration of the approximate original grade. C. Layered fabric stabilisation system. This system results in a slope similar to Option B, but involves the use of parallel horizontal layers of soil backfill separated by a geotechnical fabric, which acts to greatly reduce the vertical mass movesient of soil. The amount of excavation needed and both the short-term and long-term effects are very similar to those of the cribbing method, as are tho greater expenses involves. D. This method nalces use of a total retaining wall system, with nearly vertical faces and nearly level beds for planting of landscape and screening siaterials. This system would have a major visual impact from the lake, and the track record of similar installations on the lakeshore has shown that they are rarely screened so as to be unobtrusive. Depending on the method of construction and design, this system would have fair to good long term stability. The potential short-term effects of erosion due to bare ground would be relatively minimal as compared to other methods. E. This system makes use of a single 3-4* height retaining wall at the edge of the flat lawn area, which allows the slope from the base of the retaining wall to the lakeshore to be somewhat flatter than Options A through C. Another version of this option would be to construct a retaining wall of a greater height so that the slope fr n its base to the lake would meet the 2:1 standard desired. Obviously, the greater the height of such a wall, the greater the visual impact it will have from the lake. Stability also decreases as the height of such a wall becomes greater. The short-term and long-term effects on lake water quality are similar to those of Options B and C. i; -rV.-