Can I build, drive or park on top of a septic drainfield?

No. EPA advises never parking or driving on a drainfield, because the weight can crush pipes and compact the soil that treats wastewater. Keep trees far enough away that roots cannot get in, and send roof drains and sump pumps away from the field so extra water does not flood it. In Texas, structures must also stay at least 5 feet from tanks and standard drainfields under Table X. For a home delivered by truck, plan the delivery path and crane or trailer position so heavy equipment does not cross the field or tank, and mark the system before any site work begins.

Check your local rule. This varies by state, county or city. Your permitting office has the final word; the official lookup pages below show you who that is.

Sources

• How to Care for Your Septic SystemU.S. Environmental Protection Agency
• 30 TAC §285.91(10), Table X: Minimum Required Separation Distances for On-Site Sewage FacilitiesTexas Register (via The Portal to Texas History, University of North Texas)