Learn About Grading

Grading involves reshaping the ground surface to planned grades as pre-determined by and engineering survey, evaluation, and layout. Grading provides:

A more suitable topography for buildings, facilities, and other land uses
Helps to control surface runoff, soil erosion, and sedimentation during and after

Grading is a good choice in sites that are uneven or steep topography or easily erodible sils, because it stabilizes slopes and decreases runoff velocity. Grading activities should maintain existing drainage patterns as much as possible.

Before grading activities begin, decisions must be made regarding the steepness of cut-and-fill slopes and how the slopes will be protected from runoff, stabilized and maintained.
A grading plan should be prepared that establishes and includes:
• Identification of areas of the site to be graded
• How drainage patterns will be directed
• How runoff velocities will affect receiving waters.
• Information regarding when earthwork will start and stop
• The degree and length of finished slopes
• Where and how excess material will be disposed of (or where borrow materials
will be obtained if needed).
• Berms, diversions, and other storm water practices that require excavation and
filling should be incorporated into the grading plan.

A low-impact development BMP that can be incorporated into a grading plan is site fingerprinting, which involves clearing and grading only those areas necessary for building activities and equipment traffic.

Maintaining undisturbed temporary or permanent buffer zones in the grading operation provides a low-cost sediment control measure that will help reduce runoff and off-site sedimentation. The lowest elevation of the site should remain undisturbed to provide a protected storm water outlet before storm drains or other construction outlets are installed.

Improper grading practices that disrupt natural storm water patterns might lead to:
• Poor Drainage
• High Runoff Velocities
• Increased Peak Flows during storm events

Clearing and grading of the entire site without vegetated buffers promotes:
• Off-site transport of sediments and other pollutants.

The grading plan must be designed with erosion and sediment control and storm water
management goals in mind; grading crews must be carefully supervised to ensure that the plan is implemented as intended.
All graded areas and supporting erosion and sediment control practices should be periodically checked, especially after heavy rainfalls. All sediment should be removed from diversions or other storm water conveyances promptly. If washouts or breaks occur, they should be repaired immediately. Prompt maintenance of small-scale eroded areas is essential to prevent these areas from becoming significant gullies.

Land grading is an effective means of reducing steep slopes and stabilizing highly erodible soils when properly implemented with storm water management and erosion and sediment control  practices. Land grading is not effective when drainage patterns are altered or when vegetated  areas on the perimeter of the site are destroyed.

Land grading is practiced at virtually all construction sites. Additional site planning to incorporate storm water and erosion and sediment controls in the grading plan can require several hours of planning by a certified engineer or landscape architect. Extra time might be required to excavate diversions and construct berms, and fill materials might be needed to build up low-lying areas or fill depressions.