Shallow Gravelless Drainfields are the ideal subsurface dispersal method for highly-treated effluent. In the typical "septic tank to drainfield" system, drainfields are generally 24" deep or more and require costly excavation and rock fill. But because of its exceptionally high quality, the effluent produced by textile or sand filters can be absorbed at higher rates than other wastewater and can be discharged to shallow trenches.
Shallow trenches reduce installation costs and minimize site impacts, virtually eliminating the need to remove existing trees and vegetation. Moreover, in most states, shallow trenches can be smaller in total area than the typical drainfield. Most importantly, shallow trenches provide additional treatment of (and nutrient removal from) effluent. In fact, our research studies indicate that an additional 50% reduction in total nitrogen occurs in shallow trenches.