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Nationwide Insurance - Center for Radiation Oncology, 7315 Green Slope Drive, Zephyrhills, FL Lab No, 190442 Page 11 The hand auger borings and SPT borings found clayey sands to occur at shallow depths beneath the site and laboratory testing found them to be at the lower end of the moderate plasticity range. However, some of these soils would be considered marginally expansive based on the current Florida Building Code, and should be taken into consideration when designing a shallow foundation system bearing in these soils. We do not know if this was taken into consideration when the building was constructed. The building is located on the side slope of a hill which slopes downward to a retention pond, and the soils underlying the site would be subject to fluctuating moisture conditions. Variations in the moisture content are capable of causing volume changes to occur within these clayey soils and to cause minor damage to an overlying structure. The minor cracks/separations noted in the windowsills are in joints between the precast sill sections and are not the result of settlement of the building. Two of the four SPT borings did find evidence of sinkhole activity with drops of the drill rod, raveled soil zones and associated losses of drill fluid circulation. Boring B-1, which was drilled by the primary cause of concern encountered a raveled zone from 48 feet to 61 feet with small WOH and WOR zones encountered. A partial loss of drilling fluid occurred well above the limestone, in the raveled zone, at 50 feet indicating the presence of a void or a hydraulic connection to the underlying limestone formation that would facilitate a downward migration of soils. Boring B-3, which was drilled near the northwest comer of the building encountered a large raveled zone from 56 feet to 84.5 feet and recorded multiple WOR and WOH drops ranging from 2 to 8 feet. A complete loss of circulation occurred near the top of this zone indicating the presence of a void or a hydraulic connection to the underlying limestone formation that would facilitate a downward migration of soils, causing a loss of bearing capacity. This sinkhole activity is capable of having weakened the soil profile to the extent in which ground subsidence has occurred and contributed to the damage observed. In conclusion, it is our opinion based on the data generated in this comprehensive geotechnical investigation, that active sinkhole conditions are present beneath the site and cannot be ruled out as a contributing factor to the damage observed. Recommendations As noted above, since sinkhole activity was found beneath the building and may have contributed to the damage observed, it is our opinion that remediation of the sinkhole activity should proceed as follows: 1) The deeper portions of the soil profile that have been effected by sinkhole activity can be stabilized by a program of subsurface grouting where a cementitious grout mix is pumped under low to moderate pressures beginning at the upper surface of the competent rock and progressing upward through the raveled soil zones toward the surface. If the deep subsurface stabilization is undertaken, the grouting should be performed around the perimeter of the building with the points alternately angled toward the center of the building. The deepest installed injection point should be pumped first with successive points from deepest to most shallow being pumped afterward. All injection points should be installed prior to the commencement of the pumping. Central Florida Testing Laboratories, Inc. 12625 - 40th Street North, Clearwater, FL 33762