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Thirty-two (32) vertical and angled grout injection points are recommended at the locations shown on Figure 6. The grout casings should be installed into firm limestone bedrock or a competent soil stratum, which is estimated to occur at depths of 45 to 60 feet below grade based on the SPT borings completed at the site. Due to the local zones of very soft and raveled soils, appropriate drilling equipment should be utilized to ensure the grout injection pipes are installed to the required depths. During grout point installation, care should also be taken to identify the soil materials to ensure the grout pipes are not installed to depths significantly below the limestone surface, and should be limited to a maximum 10 feet into the limestone formation or a maximum depth of 70 feet below the ground surface without prior approval from the Engineer. The angled drill points should be installed at the appropriate angle to direct material under the structure footprint. The specific angle for individual points should be determined based on the structure dimensions and depth to competent bearing stratum at the site. We note that additional, intermediate grout points may be necessary if high grout volumes are recorded during the grouting program. In order to improve stabilization of the shallow sandy soils, use of progressively lower injection pressures may be needed at shallow depths. Around the structure, grouting should continue to a depth of 10 feet below the ground surface. During mobilization and prior to grouting, particular care should be taken to identify subsurface obstructions at the site that could potentially be damaged (underground utilities, septic tanks, water wells, etc.). 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 �routin�pumpin� rate is l 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 building and adjacent structures during grouting. 4.2 Chemical Grouting In order to stabilize the shallow loose soils underlying the building 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 5�;1,�;ic�e�ce I�Erest�gatia�-. �C1 I'��oiec; f�o. t}� l�bl� �}i`<ill4f� :��C?SS:;71 ��ils�iil�SSOC:1tt�ItT31Il�;i'{?2'ziC)f"c'it�C� fil7(i; ,'QfG� ��t>iSil T`�Cr. 3�'t��,_'.jc�'rF ��el.'f: ��i