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If this approach is used and the excavation bottoms terminate in non-free draining granular <br /> soil we recommend a drain tile be installed along the bottom outer edges of the excavation to <br /> collect and remove any water that may accumulate within the sand. The bottom of the <br /> excavation should be graded away from the building. <br /> If the banks of the excavations to remove the frost-susceptible soils are not sloped, abrupt <br /> transitions between the frost-susceptible and non-frost-susceptible backfill will exist along <br /> which unfavorable amounts of differential heaving may occur. Such transitions could exist <br /> between exterior slabs and sidewalks, between exterior slabs and pavements and along the <br /> slabs themselves if the excavations are confined to only the building entrances. To address <br /> this issue we recommend sloping the excavations to remove frost-susceptible soils at a <br /> minimum 3:1 (horizontal:vertical) gradient. <br /> Another alternative for reducing frost heave is to support the slabs on frost depth footings. A <br /> void space of at least 4 inches should be provided between the slab and the underlying soil to <br /> allow the soil to heave without affecting the slabs. <br /> 4.7 Site Grading and Drainage <br /> We recommend the site be graded to provide positive run-off away from the proposed <br /> building. 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 /> 5.0 CONSTRUCTION CONSIDERATIONS <br /> 5.1 Excavation <br /> The soils encountered in the borings,at the anticipated excavation depths,consisted of mostly <br /> granular soils consisting of silty sand and sandy silt which corresponds to the ASTM <br /> Classifications SM and MLS,respectively. The soils identified in the borings will generally be <br /> Type C soils under Department of Labor Occupational Safety and Health Administration <br /> (OSHA) guidelines. Temporary excavations in Type C(sand)soils should be constructed at a <br /> minimum of 11/2 foot horizontal to every 1 foot vertical within excavations. Slopes constructed <br /> in this manner may still exhibit surface sloughing. If site constraints do not allow the <br /> construction of slopes with these dimensions then temporary shoring may be required. <br /> 5.2 Observations <br /> A geotechnical engineer should observe the excavation subgrade to evaluate if the subgrade <br /> soils are similar to those encountered in the borings and adequate to support the proposed <br /> construction. <br /> 6 <br />