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• The result§ of the SPT borings indicate the presence of a clayey subsoil at depths of 12 feet below grade which are potentially subjected to the fluctuation of the water table. With changes in moisture content at the given depth and compositional variations in the clayey soils across the property, some minor differential settlement may be expected. This differential movement may result in widespread areas of cracking and cosmetic settlement distress to the building structure. • The small ground depression identified on the south side of the house was tested by boring SPT -2, which found evidence of unstable and possibly raveled soil conditions. Given these results, the depression appears to be related to the settlement of locally disturbed surficial soils and appears to be related to deeper soil conditions. Overall, the current level of settlement distress to the house is generally minor and cosmetic in nature. However, remedial measures to stabilize the structure against further sinkhole related settlement should be implemented. These should include a program of compaction grouting to address the subsurface zones of loose and apparently raveled soils underlying the structure. Since the grouting will likely not be fully effective in stabilizing the shallow loose sands directly below the foundation, a program of shallow chemical grouting is also recommended. The floor elevation survey and limited cracking distress indicate the house has not been subject to significant differential settlement. Given these conditions, foundation underpinning to re -level the structure is not necessary. We also recommend that rain gutters with downspouts that discharge rainwater a minimum of 5 feet from the foundation be installed on all roof drip edges. A remediation plan is included with this report. 5.0 REMEDIAL MEASURES 5.1 Compaction Grouting A program of subsurface compaction grouting is recommended to stabilize the Barker residence against further sinkhole or karst- related settlement. The intent of the grouting is to stabilize the raveled and very soft soil zones that may underlie the house and to seal and fill the karst- related fractures and/or cavities in the underlying limestone bedrock surface. The recommended grouting program should consist of a series of vertical and angled grout injection points around the perimeter of the house. A low slump grout (3 to 5 inches) should be utilized to ensure effective treatment of the loose soil zone(s) and reduce migration of grout beyond the affected areas. Eighteen (18) 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 55 feet below grade based on the three 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 65 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.). Subsidence Investigation BCI Project No.: 19 -17094 Barker Residence March 2009 Claim No.: 3428 Page 8