Leach Field and Commercial Herb Production

I have a nice sunny spot atop my leach field and would like to know if there are any plants that I can grow for commercial use without disrupting the effluent pipes underneath. Is lavender a good choice? I live in Zone 5.
Any advice you could give would be greatly appreciated.

You should avoid herbs with deep roots that may grow into, and obstruct, weeping pipes. Perennial herbs with long tap roots such as comfrey and burdock can easily penetrate anything a meter below the surface. But many herbs have shallow root systems that do not pose a risk to the pipes as long as the pipes are 50 cm (2 feet) deep or more. Lavender, and others from the same family – including basil, thyme, sage and others – are safe to plant. Other safe possibilities are dill, fennel, parsley, savory, mint, chives, and oregano.
You need to address the possible contamination of the herbs by effluent. If the weeping pipe system is working properly there is little risk of effluent rising to the surface, but that is something you need to check and monitor. If the system is not functioning properly it is possible for effluent to seep to the surface and contaminate the crop. You should check local laws and organic certification rules concerning the practice of growing on weeping pipe fields – some jurisdictions or certifiers may forbid the practice.