04/25/96 Agenda & Packet - Laserfiche WebLink

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AET #95-1343 - Page 6 • Cause of Past Movements We judge that the majority of the past ground movements would be associated with consolidation of theP eat swamp deposits, largely due to the weight of the overburden fill. Because the fill includes some organic soils, we anticipate some compression of the fill has also occurred although to a significantly lesser degree than the major swamp dept.--In-addition to the so consolidation, the potential for soil frost heaving and ice lease formation may be contributing to the ground movement problem. RECOMMENDATIONS - ATHLETIC FIELD Although our evaluation lacks site specific laboratory testing, we estimate that future park settlements without additional regrading should be about 3" to 4" over the next 20 years. Local frost movements may also occur, which would add to the surface irregularity. Minimal grading may be needed to attain a reasonably level playing surface, and if grading remains within about e 1/z of the existingsurface settlements should remain within about l '. Variation of load surface, due to the minor grading may result in the need for on-going maintenance. Also, this type of future correction would not improve surface stability (if this is important). In the event you wish to improve future performance beyond that described, several options could be considered. These are as follows: Surcharge Option In order to reduce the consolidation potential of the swamp deposits, it would be possible to place a surcharge upon the athletic field area thereby precompressing the materials prior to final grading. To reasonably surcharge the materials, we would suggest a minimum surcharge height of 3' to 4' above the eventual final grade, and allowing the surcharge to rest for several years prior to removal. It would be possible to provide a level surcharge and sod the land for athletic field use during this time, although movements should be expected. If such movements were deemed tolerable, you could elect to leave the surcharge in-place and use the field "as is". However, we suspect the primary • and secondary consolidation which would result would be