If you don’t have a crawl space but have a partial basement you want to make deeper, you can expect to spend a little less—between $40,000 and $90,000 on average. However, if you’re not adding new finished square footage, you won’t see much in the way of ROI.

The best type of soil to build on is a mixture of sand and clay, known as loam soil. Loam soil has the best combination of these soil types to build a foundation on. The clay particles help with water retention, so it won’t erode like sandy soil might, and the sandy particles help with drainage, so you won’t see unsafe soil expansion or have an increased risk of leaks from water sitting against your foundation.

Prior to excavation, you should prepare the dig site and call 311 before you sign anything.

To get your site ready for excavation, you should move anything in the area that isn’t affixed to the land. You can save money on the excavation by removing hardscaping, including walkways, decks, concrete patios, and paver patios.

Before you carry out any digging, you should call 311 to confirm that there are no utility lines running through your excavation site. Skipping this step could lead to severe injury and property damage if your excavator hits a water, sewage, or gas line.

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.