04/25/96 Agenda & Packet - Laserfiche WebLink

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• AET #95-1343 - Page 7 differential in nature such that surcharge removal would be more desirable. If the surcharge is removed to a similar elevation as currently exists, movements should still be expected, although should be noticeably lower. Lightweight Fill Replacement Option A second option which can reduce settlement and provide a more uniform and stable playing surface would be to excavate all existing fill soils to the top of the swamp deposits and replace these materials with a lightweight fill, such as wood chips. The upper several feet of the subgrade should then be capped with a mineral soil (such as on-site sandy soils with any organic inclusions separated and discarded). The upper portion of this cap should be "topsoil" material to support vegetation. The soil should have a uniform thickness on the order of 2' to aid stability. We recommend the use of wood chips which are free of leaves and twigs. Some decomposition of the wood chips will likely occur with time, mainly were they are present above . the around water level. However, wood chips/organic soils would be consistently present below the uniform soil cover layer such that decomposition movements should generally be uniform. RECOMMENDATIONS - PARKING LOT The existing subgrade is considered unsuitable for support of a new bituminous pavement system. Correction will be needed to prevent premature pavement break up. Although the borings did not extend deep enough to evaluate peat thicknesses, it does appear peats are likely present below the upper fill soils and therefore, settlements of the parking surface should be anticipated. It is typically not feasible to excavate the compressible materials, but rather prepare the surface to proper stability as needed and live with the surface movements. The in-place profile is judged to be relatively unstable, and instability likely increases with depth. For automobile parking lots, it is normally desirable to attain a high level of stability . within the upper 21/2' subgrade zone. It will likely not be feasible to subcut to the lower portion of the zone and expect to scarify and dry the in-place soils to proper stability. Due to this, it