GeneralConstruction scheduling involves the coordination of three construction-planning activities: Site Phasing, Limiting Site Disturbance, and Construction Sequencing. Site phasing reduces erosion from a site by reducing the amount of soil exposed at any one time by staging construction activities. Limiting site disturbance preserves areas that are highly susceptible to erosion and maintains them as vegetated areas. Construction sequencing involves planning land disturbance activities to coincide with the installation of best management practices.
These tools, when combined, reduce land disturbance, protect highly erodible areas, provide for timely installation of necessary erosion control practices, and promptly restore protective cover after disturbance. The result is that the disturbed soil is left exposed for a shorter period of time, significantly reducing soil loss.
- Widely applicable and effective
- May preserve wildlife habitat and be aesthetically pleasing if properly implemented, which can increase property values
- Requires good communication between contractor, developer, and designer to ensure that the schedule is realistic and properly implemented
- May require that certain activities be performed multiple times on different portions of the site
Site PhasingSite phasing involves planning construction activities so that land disturbance is performed in stages. Rather than disturbing an entire site, only those areas under active construction are disturbed. Subsequent areas are then cleared as the construction process progresses, while previously disturbed areas are stabilized with surface protection techniques. The soil surface is left exposed and unprotected for shorter periods of time, resulting in a significant reduction in soil loss. Therefore, fewer erosion control practices are required, which may also reduce maintenance requirements and costs.
Limiting Site DisturbanceLimiting site disturbance is a planning tool that can significantly reduce soil loss from a site. Early in the planning process, highly erodible areas, such as steep slopes and unstable soils, can be identified. Those areas can be designated as undisturbed and protected during construction to prevent soil loss. Undisturbed areas may also act as buffers, reducing runoff velocities and reducing soil loss when compared to disturbed conditions.
Construction SequencingConstruction sequencing requires the developer or planner to consider all facets of site preparation and construction, including sensitive areas of the site, before any work is performed. A construction sequencing plan is created by compiling a list of the practices to be installed and a list of construction activities to be performed. The two lists are then combined to determine what activities must be in place before other activities begin. The result is that all erosion control practices are in place and online before any land disturbance activity begins, reducing erosion from the site.
Considerations for Construction Sequencing
|Construction Activity*||Schedule Consideration|
|Construction access - Construction entrance, construction routes, equipment parking areas||First land disturbing activity - stabilize bare areas immediately with gravel and temporary vegetation as construction takes place.|
|Sediment traps and barriers - Basins, traps, silt fences, and outlet protection||Install principal basins after construction site is accessed. Install additional practices as needed during grading.|
|Runoff control - Diversions, dikes, and outlet protection||Install key practices after principal sediment traps and before land grading. Install additional practices during grading.|
|Runoff conveyance system - Stabilize stream banks, storm drains, channels, inlet and outlet protection, channels, and slope drains||Where necessary, stabilize stream banks as early as possible. Install principal runoff conveyance system with runoff control measures. Install remainder of system after grading.|
|Land clearing and grading - Site preparation, cutting, filling and grading, sediment traps, barriers, drains, diversions, surface roughening||Begin major clearing and grading after principal erosion control practices have been installed. Clear and grade only as needed. Install additional measures as necessary. Mark trees and buffer areas for preservation.|
|Surface stabilization - Seeding, native grasses, mulching, sodding, and riprap||Apply temporary or permanent stabilization measures immediately on all disturbed areas where work is delayed or complete.|
|Building construction - Buildings, utilities, and paving||Install necessary practices before work takes place.|
|Infiltration Practices - bioretention basins, infiltration basins, rain gardens, infiltration trenches/beds||Must be installed during final stabilization or when runoff can be diverted and prevented from disturbing the site to avoid being filled with sediment during construction.|
|Landscaping and final stabilization - Topsoiling, trees and shrubs, seeding, mulching, sodding, riprap||Last construction phase - Stabilize all open areas, including borrow and spoil areas. Remove and stabilize all temporary practices.|
Construction and Maintenance
- Remove all temporary practices after the site has been permanently stabilized
- Amend the schedule as needed to account for delays encountered during construction