In the United States, a depth of 36 inches (three feet) for underground water lines is the accepted industry standard. This depth varies from location to location based on local conditions. In areas with colder winters, they may be buried deeper to prevent frozen well water pipes : This is usually at least six inches below the frost level. The International Plumbing Code calls for a minimum of 12 inches below grade.

There is no standard depth for burying a septic tank; they are typically buried anywhere from 4 inches to 4 feet underground. The final depth depends on several factors, including the depth of your main sewer line, the height of the bedrock, soil type, local regulations, and the property's landscape. If you plan to grow grass or plants over the tank, a depth of at least 4 to 6 inches is recommended. Deeper tanks can be more difficult to locate, but a septic professional can help find it for you.

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.

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.