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May 6, 2015
<br />Page 5 of 1 1
<br />2. Initial Site Preparation:
<br />This analysis is based upon the foundation systems being, as indicated earlier, composed of
<br />exterior and inferior strip footings. Proposed slab elevations are 912.75 and 916.0. Depth of
<br />perimeter footings is assumed for now fo be 4 foot, and interior foofings will be 1'/s foofi
<br />below slap grade (deeper if necessary fio add confinemenfi).
<br />Any unsuitable soil in the proposed building pad areas should be removed, in an
<br />oversized manner as or if necessary. Wherever encountered, the bituminous pavement
<br />should be removed and recycled. There does not appear to be any salvageable aggregate
<br />base material below. The various other unsuitable soils noted earlier, predominantly in the
<br />southwest building area, should be removed to varying depths ('/z foot — 2 foot).
<br />However, as this area appears randomly disturbed, other, possibly deeper, zones of
<br />unsuitable soil may be encountered which should be removed as well. Firm naturally
<br />occurring mineral soils should be achieved. A preliminary analysis indicafies thaf, for the
<br />northwest building, the base of excavation will be below infierior footings and below
<br />perimeter footings in the two westmost borings. For the southeast building, additional
<br />cutting for foundations, particularly trenching for exterior footings, will be necessary; only
<br />at a few of the lower elevation borings will a void result below interior footings.
<br />In the vicinity of Borings 4& 5, there should be very close inspection of soil exposed,
<br />including frequent hand auger borings. Boring evidence indicates that first mineral soil
<br />encountered will be firm, and that the noted wet and softer soil will be "one footing
<br />width" or more below footing level. This will not significantly affect footing performance due
<br />to separation and the relatively fhin thickness of these zones. However, if fhese materials
<br />are indeed encounfiered in this noted zone, fhey should be subcut out, in an oversized
<br />manner, as necessary.
<br />Oversizing of any excavation below footings will be necessary for proper lateral
<br />stability of the fill. As indicated by #5 below, this oversizing should be 1:1 from footing
<br />level. Once this excavation has been accomplished, any void below planned foundation
<br />and slab areas should be restored with controlled fill. Perimeter footings could be lowered
<br />somewhat, beyond their typical levels, to minimize this oversizing or to achieve better
<br />soils and eliminate the supplemental subcut. But the interior of the building pad area will still
<br />have to be built up to grade with controlled fill.
<br />Remnants of a former building on the site may be encountered. It could be old foundations
<br />or loose foundation trench voids, possibly and isolated basement or pit void. These zones, if
<br />encountered, will have to be subcut out and resulting voids refilled in a controlled manner.
<br />If any water, be it perched groundwater or rainfall, interferes with construction, it should be
<br />controlled during foundation construction, perhaps by a method such as sumping. If worker
<br />traffic tends to destabilize footing contact soil, a few inches of stabilizing aggregate, such as
<br />clean coarse rock, could be applied to trench bottoms. If this is done, the soils engineer
<br />should inspect the contact soil prior to application of aggregate.
<br />It should again be emphasized, however, that the esfimated depfihs of excavation of
<br />unsuitable soil given above are preliminary estimafes based mostly upon random split-barrel
<br />sampler tests, which are not as accurate as auger borings. These should be considered
<br />preliminary estimates only, to be verified by actual excavations. In fact, for construction
<br />quantity purposes, a small amount of additional estimated excavation depth should be added
<br />to that given in the logs to conservatively allow for variations and for inadvertent over-
<br />excavations which are impossible to avoid when power machinery is employed for the
<br />purpose. It is especially cautioned again that, since this site has been already altered, there
<br />could be areas of unsuitable soil not represented by the borings to date. These zones could
<br />additionally include old trash pits, test excavations, utility trenches, etc. Excavators should be
<br />especially aware of this possibility.
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