Subgrade Level — How To Plan Drainage
Define the finished purpose, reference levels, underlying material condition and the evidence required by the receiving operation. Geometry alone does not establish structural or agronomic performance.
This reference assembles relevant extracts from the guide library. It is general project planning, not a local project report, verified specification or translated technical publication.
Drainage Grade Design
Drainage grade design must connect the contributing area to a suitable outlet. Selecting a numerical fall before checking the outlet can produce a surface that cannot discharge as intended.
Before moving material
Survey entry points, structures and the receiving level.
Receiving operation and checks
Inspect the constructed route and its transitions. Check invert continuity and controls at crossings.
This guide does not size drains or establish discharge permissions.
Read the complete Drainage Grade Design guidePoor Surface Drainage
Poor surface drainage can result from a blocked outlet, a reversed fall, a damaged crossing or local depressions. Grading should follow the identified cause.
Before moving material
Trace water from its entry point to the receiving outlet.
Receiving operation and checks
Inspect the drainage route during a suitable water event. Check that the complete route remains connected through boundaries and crossings.
Surface grading cannot remedy every subsurface drainage problem.
Read the complete Poor Surface Drainage guideUneven Subgrade
Uneven subgrade can create variable thickness in every layer above it. Correcting the surface is useful only if the underlying support is acceptable.
Before moving material
Identify soft areas and compare formation levels with design.
Receiving operation and checks
Complete compaction and specified acceptance checks. Check levels before base material conceals the subgrade.
A scraper does not replace proof testing or project-specific investigation.
Read the complete Uneven Subgrade guideRecord the job inputs
Use this checklist to turn the scenario into a specific brief. Retain the design revision and agree who accepts each completed layer.
Checklist ticks apply only while this page is open. Include the completed brief in your project records.
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