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i <br /> I Soil specimens were reviewed and classified in the soil laborato b th <br /> ry y e geotechrncal engineer. . <br /> I Boring Logs were prepared with respect to ASTM D2488 (Description of Soi/s: Visual and Manual <br /> Procedure). Soil strata lines shown on the Boring Logs are approximate boundaries between <br /> different soil types. Transition between soil types may be gradual. <br /> I <br /> SUBSURFACE CHARACTER <br /> I <br /> GEOLOGY <br /> The project site is in an area subject to at least four major continental glaciations, each lasting over <br /> . 100,000 years. The glaciations occurred from the late Pliocene Epoch 2.5 million years ago to the <br /> end of the Pleistocene Epoch 10,000 years ago. Climate fluctuations created glaciers from several <br /> ! hundred feet up to a few miles thick that flowed across the North American landscape. Periodic <br /> ' climate waRning gradually stopped the flows and glacial ice stagnation set in. SurFaces of the <br /> glacial ice sheets melted, creating streams and lakes filled with glaciai sediment (supraglacial <br /> deposits) on ice sheet surtaces. Glacial meltwater on ice surtaces flowed into crevasses and <br /> fractures or flowed to the glacier's margin. Lakes often formed along margins of the wasting ice <br /> sheet. Glacier wasting may produce large chambers under ice�Iled with water. Advanced wasting <br /> of the glacier left remnant ice blocks buried in glacial sediment. When the blocks eventually <br /> melted, depressions (kettles) were formed on the ground surface occupied by lakes. Complete <br /> wasting of glacial ice left glacial sediment (glacial drift) upon the landscape. <br /> The most recent continental glaciation (the �sconsinan) began around 115,000 years ago near <br /> the close of the Sangamon interglacial warm period. During Wisconsinan time, maximum giacial <br /> cold and glacial ice advancement occurred around 24,000 years ago. Fingers (lobes) of glacial ice <br /> ' flowed off the margins of the greater �sconsinan continental glacial ice sheet. For example, the <br /> Superior Lobe glacial ice sheet flowed southward from the Lake Superior region into the Twin <br /> Cities area, depositing significant reddish sandy sediment. Thereafter, the Des Moines Lobe <br /> flowed across the eastem Dakotas and Minnesota down to the Raccoon River in Des Moines, <br /> lowa, where it stopped and stagnated nearly 16,000 years ago. The Des Moines Lobe eventually <br /> wasted in Minnesota nearly 12,000 years ago and disappeared by 9,000 years ago leaving glacial <br /> drift across large portions of Minnesota. ' <br /> In Minnesota, the Wisconsinan age glacial drift is deposited upon older glacial drift of Pre- <br /> �sconsinan age. Glacial drift is generally comprised of glacial outwash and glacial till <br /> (supraglacial till or subglacial till types). Glacial oufinrash sediment is deposited along edges of <br /> stagnant glacial ice sheets and outward from glacio-fluvial streams flowing from the sheets. <br /> Outwash is often grain size-sorted with stratified bedding and more rounded grain shapes. <br /> Coarser outwash (sand and gravel) is often deposited near ice margins, while finer outwash (silt <br /> and clay) is often deposited farther away from ice margins. Supraglacial till is derived from glacial <br /> meltwater sediment deposited upon the surFace of the wasting glacial ice. Subglacial till is derived <br /> from glacial debris deposited along the bottom of the flowing glacier. This debris is from <br /> Allied Projed 05039 3 July 31, 2005 <br />