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Subsidence lnve,stigation SDII Project Number:3023547 Quiros-Martin�;;z Residence-Zephyrhills,Florida capacity of structural members or systems. The damage to the residence is considered cosmetic in nature. 3.6 Sumnrary of Structural Evaluation It is SDll's opinion, with reasonable professional probabiIity, that the damage to the residence is consistent wi1:h normal shrinkage cracking of un-reinfarced or mildly reinforced concrete and masonry; min�r differential foundation movement; long-term deflection of the roof structure; post-construct�on structural settlement; and minor thermal and moisture induced volume changes of construction materials including gypsum board, wood trim and framing, stucco, and fasteners. The lack of si,�fficient footing embedment may have contributed to the damage. The observed damage on th�:; exterior and interior of the residence is cosmetic in nature, such that the design function of the;building has not been compromised. 3.7 Remeclial Recommendations The geologic a.nd geotechnical investigations concluded that sinkhole activity is occurring at the site. It is our recommendation that the subsurface soils be stabilized to minimize further subsidence damage. Stabilization should be accomplished through compaction grout injection to densify the so�ls beneath the residence and to seal the top of the limestone surface to minimize future raveling;. The compactiun grout stabilization should incorporate 15 injection points spaced approximately 10 feet on center around the perimeter of the structure. The grout points should be vertical and inchned as shcrwn on Figure 6. Grout point locations should be as close to the perimeter of the structure as po�;sible. The depth of�;routing, based on the field boring logs, is likely to vary from approximately 50 feet in the viciriity of boring B-1, to 60 feet in the vicinity of boring B-3, to 65 feet in the vicinity of boring B-2 (�estimated average depth of 60 feet). The overseeing geotechnical engineer should approve the ad vancement of any injection point deeper than 75 feet. Grout injection should be performed up 10 a depth of 15 feet unless otherwise specified by the overseeing geotechnical engineer. Typical pre-mi xed compaction grout, with sufficient silt sizes to develop internal friction that generally does not enter soil pores but remains in a homogenous mass that can give controlled displacement bc� loose soils, with a slump between 4 and 6 inches, should be used. The grout should be pum�ed at slow enough rates such that the grout will densify and not merely hydro- fracture the soiL The injection pressures (at in-line pressure gauge at, or just before, the top of the grout pipe;� should be limited to 300 pounds per square inch (psi). Additionally, no more than 10 yards c�f grout should be injected into any single point within a six-hour period. The elevation of th�� structure, and any within 30 feet of the injection point, should be monitored continuously di��ring the grouting process to minimize unnecessary upward movement. 3-4