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Subsurface Exploration and Foundation Evaluation
<br /> Proposed Golden Oil Refueling Station
<br /> Stoughton, Wisconsin
<br /> PSI Project No. 0092822
<br /> Page 6
<br /> existing pavement, topsoil, topsoil fill, buried topsoil, vegetation, trees, roots and other organic
<br /> matter must be stripped from the areas of footings, floor slabs, pavements, sidewalks, and
<br /> other structures.
<br /> Site preparation will require removal of the existing structures and remnants of former
<br /> buildings, including foundations, underground utilities and underground storage tanks.
<br /> Extensive areas of loose backfill material may be encountered within utility trenches, adjacent
<br /> to the existing structures, and in former building and basement areas. These will also require
<br /> removal. The areas, including basements and former underground storage tanks, must then
<br /> be properly backfilled with compacted structural fill. Prior to the backfilling, the areas must be
<br /> observed by an PSI representative to evaluate the suitability of the subgrade for subsequent
<br /> support of the new building, utilities, or other structures.
<br /> Topsoil depths or otherwise unsuitable organic soils may increase substantially within and
<br /> encroaching upon wetland areas. It is generally recommended that development within
<br /> wetland areas not be performed due to the typical presence of highly organic soils and shallow
<br /> groundwater. If such development is contemplated, special permits will likely be required from
<br /> the Army Corps of Engineers, the WDNR, or other government agencies.
<br /> After stripping the topsoil and cutting high areas of the site to the planned finished grade, and
<br /> prior to the placement of new fill which may be placed to raise grades, the subgrade must be
<br /> improved by surface compaction with a minimum of 10 overlapping passes (2 sets of 5 at right
<br /> angles) with a heavy (minimum 10-ton static weight) compactor. The subgrade must then be
<br /> thoroughly proofrolled to detect unstable, yielding soils, which must be removed or improved
<br /> by appropriate preparation and compaction techniques. Proofrolling should consist of
<br /> overlapping passes in a perpendicular grid pattern of a fully-loaded tandem-axle dump truck,
<br /> or other equipment of similar size and weight. However, care must be used on this site to
<br /> avoid disturbing the near surface fine-grained soils during the proofrolling, especially during
<br /> periods of precipitation or spring thaw. Proofrolling with rubber tired equipment may be
<br /> preferable, but should be performed in consultation with the geotechnical engineer at the time
<br /> of construction. Loose, soft, unstable, or otherwise unsuitable soils should be expected,
<br /> especially within existing fill. When encountered, they must be removed and replaced with
<br /> compacted structural fill. Scarification, drying and recompaction of wet soils or removal and
<br /> replacement with suitable fill, are two methods, which can be considered, but this must be
<br /> determined by the soils engineer at the time of construction. Low areas may then be raised to
<br /> the planned grades with suitable properly compacted fill.
<br /> The exposed subgrade in the building and pavement areas is expected to consist of at least
<br /> some areas of cohesive soils. Such soils are considered highly moisture sensitive and subject
<br /> to softening. Therefore, equipment and worker traffic must be kept to a minimum on subgrade
<br /> bearing surfaces, especially during times of precipitation or following spring thaw. Some
<br /> difficulty with subgrade preparation can be expected in wet or cold weather conditions.
<br /> Removal of unsuitable portions of the near surface soils and replacement with structural fill will
<br /> likely be required, on at least an isolated basis, especially if earthwork is not carried out during
<br /> periods of relatively warm, dry weather, which provide more favorable conditions for drying of
<br /> these soils. Any soft zones, which cannot be improved by scarification and aeration, must be
<br /> removed and replaced with compacted structural fill, such as clean crushed stone, possibly in
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