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Trenches are typically 12 to 24 inches deep and 8 inches wide. However, the required depth depends on the specific project and local ordinances. For example, a French drain may need to be 18 inches deep, while a water pipe might require a depth of 24 inches and a drainage pipe 36 inches. Your city or county may have specific regulations, so it's wise to consult with an excavation professional to determine the correct depth for your project.

Because decomposed granite is a durable material, a crushed rock or gravel base is optional as long as the DG is properly installed and compacted. However, installing a base is a good idea because it will ensure proper drainage and stability and act as a weed suppressant (although you may still occasionally have to pull weeds). Installing an adequate base can also increase the durability of driveways and walkways. If you forego the paver base or gravel underneath, line the area with landscaping fabric to avoid weeds.

Septic drain lines (or leach lines) are typically buried between 18 and 36 inches underground, and should be at least 6 inches below the surface. These pipes are perforated and surrounded by filtering materials like sand or gravel. Burying the lines at this depth helps minimize odors and allows bacteria and other biological processes in the soil to effectively treat the wastewater. Burying lines too close to the surface can cause issues unless the soil is very compact and stable.

Tree experts don’t advise against digging through tree roots, but instead encourage caution and consultation with a local arborist to make sure you don’t damage the tree’s structure or interrupt its water or nutrient intake. An arborist can recommend specific practices when digging and help prune the roots or dig a trench for utilities with a tool that can remove soil without touching the tree’s roots.