Every year the same question arises: Can I plant my garden on or near the septic system? Before you can answer that question, you may need to know a little about the workings of a septic system.
A septic system has two main parts, a septic tank and a drain field (leach field). Wastewater from the home runs into the septic tank. Solids remain in the tank while liquid flows on into the drain field. The drain field is a series of underground perforated pipes set in gravel that allow the effluent (the outflow from the sewage system) to slowly drain and filter the water over a large area. During drought, it is easy to locate the leach field; it will remain green while the rest of lawn turns brown because of the moisture from the underground pipes.
So is it OK garden near the septic system? To answer that question, a few things need to be considered. 1. Can a garden be contaminated by bacterial and viral hazards which may be found in septic drainfields? A properly operating septic system will not contaminate the soil with disease organisms, but it can be difficult to tell if the system is working at optimum efficiency. Also, the soil type can make a difference. Clay-like soil will eliminate any organism within a few inches of the system, while a sandy soil could allow for movement of bacteria several feet.
Since it is difficult to be sure if your septic system is working an optimum level, I do not recommend planting a garden in this area. An ornamental, such as grass, would be a better fit for this area. But, I know many of you will still attempt to raise a garden in this area anyway. So if you do, stay away from rooting crops such as carrots or potatoes. Also avoid leafy vegetables such as lettuce or kale, since water may splash up from the ground during rains. Plants that grow up off the ground, such as tomatoes, may be a better fit. Be sure to trellis any vining crops, such beans or squash up off the ground.
2. Is it safe for the septic system to have a garden growing over it? The simple answer is no. While walking or light digging over a drain field is not a problem, plowing, tilling or building up soil for a raised bed can damage the system. According to Marvin Dixon at the Madison County Health Department, gardening on a septic system can damage components and lead to erosion in that area. He recommends gardening no closer than 10 feet from the drainfield.
With all of that in mind, I do not recommend gardening within 10 feet of the septic system. The health of you and your family is too important to be put at risk and the cost to repair a septic system is too high to chance it.
Educational programs of the University of Kentucky Cooperative Extension Service serve all people regardless of race, color, age, sex, religion, disability or national origin.