Grading activities take place after clearing the project site of demolition debris, vegetation, and top soil. Grading refers to the adjustment of site slopes to the extent required to facilitate new construction and site function, including proper storm water run-off gradients and features. Having both an existing site survey (including a soil investigation) and a new construction site plan are critical to understanding the starting topography and desired end state throughout the project area. Also important is an evaluation of the existing site soils to match new construction purposes such as foundation work, or even to facilitate temporary construction needs such as equipment movement and soil sediment control.
Excavation refers to the removal of soils below the grade elevation (ground level) at a project site. An excavation is usually a temporary requirement for the placement of foundation structures, utilities, and basements below grade. Considerations for excavation include the characteristics of the soil at the work location, the required depth and amount of soils to be removed, and any site constraints including adjacent structures and property lines. Depending on the height of the water table and the permeability of the soil being excavated, dewatering may be required if a dry work environment is necessary.
Dewatering is associated with excavations where there is a need to work in dryer soils without being affected by the water table or moisture at a project site. A decision to perform dewatering at an excavation site is determined by the elevation of the bottom of an excavation, the height of the water table, the permeability and saturation of the soils, the degree of stabilization required along the edges of the excavation, and the duration and nature of the work being performed. The type of equipment and pumps selected for a dewatering effort are also determined by these factors.
When I began my career in the engineering/construction industry 37 years ago, erosion from construction sites was never a stated concern. None of the huge water treatment plants and wastewater treatment plants I designed had any provisions for preventing erosion or controlling sediment. The streams, lakes, and rivers downstream from my sites no doubt did a lot of natural “settling” and maybe “filtration.”
