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121'06/06 WED 18:03 FAX 727 867 9455 WillinghamCompanies ~008 ..-.. ., I' ; I . , "'"" ,II. .. . ~ Zephyrhllls professional Center Site Pasco County, Florida ODE Job No, 05-432 Page' SUBSURFACE ANALYSIS Foundation Analysis Based on all the borings performed at the site, the primary soil related factor affecting the performance l)f shallow foundations for the proposed structures is the potential totnl and differential settlement due to the relatively loose sands encountered at and near ground surface. Due to the sandy nature of the near-surface soils, these settlements should occur with the application of load (either fill or structural), Foundation Recommendations Provided estimated settlements are within the structural tolerance, (X)nventional shallow foundation systems consisting of perimeter wall footings and isolated pad footings should provide adequate support for the proposed structure, assuming the complete removal of all surface organic materials, proper subgrade preparation, and proper fill placement, as described later. Based on the SPT RN" values obtained from the soil borings, a net allowable soil bearing pressure of 2,000 psf (in excess of overburden) is estimated for the existing shallow soils found over the site and for structural fill as described in this report. This bearing pressure estimate is based on the complete removal of all surface organic materials, the removal of organic materials beneath footings, and the filling and recompacting described later in this report. Settlements for the proposed structures and the anticipated fill, based on a bearing capacity of 2,000 psf. are estimated to be about 1-inch total. As discussed previously. due to the sandy nature of the materials, these settlements should occur as the loads are applied, A minimum footing width of 24 inches and a minimum depth of embedment of 18 inches should be used for footing design for all structures. RECOMMENDATIONS AND CONCLUSIONS Site Stripping Prior to any construction, the site must be properly prepared. To prepare the site for construction, all existing topsoil, muck, debris, vegetation, and large roots down to finger-size should be removed including a 5-foot margin. The resulting excavations should be backfilled with soils as discussed in the structural fill section of this report. Proofrolling Following site stripping and any related excavation activity, and prior to any fill placement, proofrolling should be performed. We recommend using a vibratory roller having a static weight of at least ten tons. Compaction of the fill materials should continue until the roller has made at least ten passes over all areas of the site and the soils appear to be relatively firm and unyielding. Half of the roller passes should be perpendicular to the direction of travel of the other passes. Proofrolling should be closely monitored by our engineering technician to observe for unusual deflection of the soils beneath the compacting equipment. If unusual or excessive deflection is obsE:rved, then the areas should be undercut to firm soils and backfilled with structural fill placed In maximum one-foot thick lifts. Backfill soils should be of the same composition and be compacted to the same criteria as structural fill soils. Structural Fill Definition Soil used for structural fill can be defined as clean fine sand containing less than twelve percent material by weight that is finer than a number 200 sieve (fines) (matelial conforming to SP to SP-SM in