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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 />Soil Type <br />Estimated <br />Unit <br />Weight <br />(pcf) <br />Estimated <br />Friction <br />Angle <br />(degrees) <br />At -Rest <br />Pressure <br />(pcf) <br />Active <br />Soil <br />Pressure <br />(pcf) <br />Passive Soil <br />Pressure <br />(pcf) <br />Sands <br />(SP & SP-SM) <br />120 <br />32 <br />55 <br />35 <br />390 <br />Clayey and Silty Soils <br />(CL and SM) <br />135 <br />28 <br />70 <br />50 <br />375 <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 />