Chapter 5
Site Grading
Learning Objective: To understand the process of site grading
its benefits, challenges, and opportunities.
The grading process - excavating, moving, manipulating, and recompacting the soil on a project is one of the most important aspects in the process of constructing lots for homebuilding. Proper placement and compaction of soils will help to ensure building foundations, road beds, sidewalks, and underground utilities will stay securely in place and not jeopardize their longevity or function. Grading shapes the site to allow surface runoff to occur without erosion or sedimentation, and/or collect runoff into basins or to divert it through the site to other collection locations. It diverts surface and occasionally subsurface flows away from buildings to prevent saturation of soils that can lead to damaged structures and weakened paving.
A. Purpose and Benefits
When the engineer designs the grading plan for a project, the objective is to create a balance of cut (excavated soil) and fill (placed and compacted soil) in order to avoid importing soil to the site or exporting soil from the site, both which can be expensive. In some cases, it is unavoidable if the quality or quantity of soils cannot be met within the existing site parameters. Methods vary, but soils engineers can determine the amount of soil compaction required for the soil profile to prevent soil movement or collapse once structures are placed upon it. In order for building lots to meet FHA requirements, unpaved areas near buildings must be graded with enough slope to force water away toward streets, swales, and other collection points.
