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A copy of our recommended specifications for the compaction grouting program and a contractor bidding form are included in Appendix E. Important provisions of the specifications include the following: • Installation of grout casings in a manner to prevent grout leakage and/or uplift of casing during grout injection. The contractors bidding the project should provide a description of their method of installing the grout casings. • Injection of a low -slump grout ranging from 3 to 5 inches, as measured at the hopper. Grout slumps as high as 5 to 7 inches may be acceptable during initial grout injection to fill and seal the limestone bedrock surface, as well as in areas of obvious soil cavities if grout takes are low. • Control of grout pumping rates and quantities, such that for each injection interval, injected grout quantities are limited to a maximum of 10 cubic yards (excluding obvious soil cavities). The recommended grouting_pumping rate is 1 to 5 cubic feet per minute. • Reduction of grouting pressures at shallower depths is recommended in order to stabilize any shallow loose soil zones. • Monitoring to limit uplift of the house and adjacent structures during grouting. 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 through the concrete flatwork or 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 -level slabs and foundation elements. The chemical grouting should be done after the compaction grouting is completed and should follow the specifications provided in Appendix E. BCI can provide a detailed design layout and qualified foundation repair contractor prior to implementing the program, if requested. In order to allow time for re- distribution and equilibration of stresses induced by the grouting programs, we recommend that final cosmetic repairs of cracking and other damage to the house not be undertaken for a period of four months following grouting. Subsidence Investigation BCI Project No.: 19 -17094 Barker Residence March 2009 Claim No.: 3428 Page 9