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Subsidence Investigation Pittman Residence - Zephyrhills, Florida son Project Number: 3017839 3.6 Remedial Recommendations The geologic and 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 grout injection to compact and densify the sandy soils beneath the residence. Grout injection is also intended to seal the top of the limestone surface to minimize future raveling. The grout stabilization should incorporate 18 injection points spaced approximately 10 feet on center around the perimeter of the structure. The grout points should be vertical and inclined as shown on Figure 6. The depth of grouting, based on the field boring logs is likely to vary from approximately 30 to 40 feet. Typical compaction grout mix with a slump between 4 and 6 inches should be used, pumped at slow enough rates such that the grout will densify and not merely hydro-fracture the soil. The elevation of the structure should be monitored continuously during the grouting process to minimize unnecessary upward movement. The total quantity of grout required can vary based on site conditions, but is likely to be between 100 and 150 cubic yards (cy). The estimated cost for repair is based on the higher volume of grout. A list of estimated costs for repair is provided below. It does not include estimates for engineering supervision during remediation, nor does it include estimates for cosmetic repairs, which should be estimated by a qualified insurance adjustor or contractor. Cosmetic repairs should be postponed for 30 to 60 days after the grouting to allow any final ground movement to occur. A. Install grout pipes: 18 @ 35 feet (avg) @ $15/ft ................................$9,450 B. Grouting: 150 cy @ $155/cy.. ........... .......... ........... ................. ............23,250 C. Site Restoration.... ...... ......... ...... ... ................. '" ... ....................... ........ 4,000 Total .............$36,700 This cost estimate should be considered an "order of magnitude" estimate of actual construction costs, and therefore should not be construed as a bid for performing the work. Actual costs can only be determined through solicitation of bids from qualified contractors. Continuous monitoring by SDU personnel during remediation is suggested to verify compliance with these recommendations and to make necessary adjustments to the remediation program due to unforeseen site conditions. This will also allow the engineer who created the remedial design to certify that the remediation met design specifications. 3-3