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The straightforward calculation for a level surface is: L x W x H. For a contoured surface, you need to create level zones on your plans and perform volume takeoffs based on those grids, using the L x W x H formula.

Here are some other things to consider when estimating foundation work.

1. Study the geotechnical report to understand the current state of the soils, and to determine using core reports at what level the foundations needs to be laid.
2. Determine the thickness of the foundation in the drawings.
3. Determine the total thickness of compacted materials necessary for the underlayment of the foundation level.
4. Excavate down to a level where corrosive materials are not present.
5. Infill with imported materials, up to the level of the foundation start, when needed and then use backfill and compaction methods to level ground before foundation is poured.

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