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Subsidence Investigation Mathew/Aley Rental Property Claim No. 223968 BCI Project No. 03-15564 November 2007 Page 11 5.2 Chemical Grouting In order to fully stabilize the shallow loose soils underlying the house foundation, a program of shallow chemical injection grouting using a specially-formulated polyurethane expanding polymer is also recommended around the perimeter of the structure. This material cures to form a durable, high strength solid grout. Injection of the grout material requires drilling %-inch diameter holes around the outside perimeter of the house on 4 to 6 foot centers, installing grout pipes, and injecting the grout under controlled pressure to fill voids, densify loose materials, and re-Ievel slabs and foundation elements. The chemical grouting should be done after the compaction grouting is completed. BCI can provide detailed design recommendations and a list of qualified foundation repair contractors to do the chemical grouting, if requested. In order to allow time for re-distribution and equilibration of stresses induced by the grouting programs, we recommend that fmal cosmetic repairs of cracking and other damage to the house not be undertaken for a period of four months following grouting. 5.3 Project Costs A cost estimate for the proposed grouting program is presented below in Table 3. As shown, project costs are estimated at $65,956. It should be noted that these costs are estimated based on our experience with similar projects in the central Florida area. Costs for any needed structural or cosmetic repairs to the house are not included in this estimate. Actual, final project costs for the grouting may be lower (or possibly higher) after the project is subject to final design, competitive contractor bidding, and any modifications during implementation. Table 3 Estimated Project Costs Subsurface Compaction and Chemical Grouting Mathew/Aley Rental Property Subsurface Comnaction-Chemical Groutin!! Ouantitv Units Unit Cost a. Contractor Mobilization I each $2,000 b. Installation of grout casings 960 feet $16 c. Compaction grout material and flowable fill 200 cubic yds. $160 (estimated) d. Chemical Grouting (includes 500 lbs. of material) 1 day $7,000 e. Additional chemical grout material 400 lbs $13 Subtotal = Engineering Supervision Inspection & oversight - estimated 12 to 14 days to complete grouting estimated $65,956 TOTAL ESTIMATED PROJECT COSTS = Cost $2,000 $15,360 $32,000 $7,000 $5,200 $61,560 Cost $4,396 In order to ensure compliance with the fmding of this study and project specifications, we recommend that BCI be retained to evaluate the contractor bids and provide project monitoring and oversight services during the grouting operations.