# Earthwork \[SIG] The earthwork objects calculate excavation and backfill volumes for foundation construction. These companion tools automatically derive geometry from a selected footing and compute quantities based on ground surface elevation. OpenBrIM provides two earthwork quantity objects: * **Structure Excavation**: Calculates the volume of earth to be removed from the original ground surface to the footing bottom * **Structure Backfill**: Calculates the net volume of fill material needed after construction, automatically subtracting structural component volumes Both objects work with any foundation type (Custom or Rectangular) and support both manual elevation input and DTM-based ground surfaces. --- # Agent Instructions: Querying This Documentation If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question. Perform an HTTP GET request on the current page URL with the `ask` query parameter: ``` GET https://docs.openbrim.org/templates/steel-i-girder-bridge-workflow/substructure-sig/earthwork-sig.md?ask= ``` The question should be specific, self-contained, and written in natural language. The response will contain a direct answer to the question and relevant excerpts and sources from the documentation. Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.