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Foundation walls or below grade (basement) walls will have lateral loads from the <br /> surrounding soil transmitted to them. Active earth pressures can be used to design the below <br /> grade walls if the walls are allowed to rotate slightly. If wall rotation cannot be tolerated,then <br /> below grade wall design should be based on at-rest earth pressures. It is our opinion that the <br /> estimated soil parameters presented in Table 5 can be used for below grade wall design. These <br /> estimated soil parameters are based on the assumptions that the walls are drained, there are <br /> no surcharge loads within a horizontal distance equal to the height of the wall and the backfill <br /> is level. <br /> Table 5.Estimated Soil Parameters <br /> Estimated Estimated Active <br /> At-Rest Passive Soil <br /> Unit Friction Soil <br /> Soil Type Weight Angle Pressure Pressure Pressure <br /> (pcf) (degrees) (pcf) (pcf) <br /> (pcf) <br /> Sands 120 32 55 35 390 <br /> (SP&SP-SM) <br /> Clayey and Silty Soils 135 28 70 50 375 <br /> (CL and SM) <br /> Resistance to lateral earth pressures will be provided by passive resistance against the wall <br /> footings and by sliding resistance along the bottom of the wall footings. We recommend a <br /> sliding coefficient of 0.35.This value does not include a factor of safety. <br /> 4.7 Exterior Slabs <br /> Exterior slabs will likely be underlain by granular(sand)soils consisting of poorly grade sand <br /> with silt and poorly graded sand. These soils are generally slightly to non-frost susceptible <br /> soils. This being the case, it is our opinion that special subgrade improvements in excess of <br /> topsoil stripping in advance of slab construction will not be required. <br /> 4.8 Site Grading and Drainage <br /> We recommend the site be graded to provide positive run-off away from the proposed <br /> buildings. We recommend landscaped areas be sloped a minimum of 6 inches within 10 feet <br /> of the building and slabs be sloped a minimum of 2 inches. In addition, we recommend <br /> downspouts with long splash blocks or extensions. <br /> We recommend the lowest floor grades be constructed to meet City of Ramsey (City) <br /> requirements with respect to groundwater separation distances. In the absence of City <br /> requirements,we recommend maintaining at least a 4-foot separation between the lowest floor <br /> slab and the observed groundwater levels and at least a 2-foot separation between the lowest <br /> floor slab and the 100-year flood level of nearby wetlands,storm water ponds or other surface <br /> water features. <br /> 10 <br />