Question:Do you need the same amount of vertical separation between the bottom of a seepage trench and seasonal high water table for effluent treated with a septic tank and effluent treated with an aerobic treatment plant? If not, what do you recommend for each? Answer:First of all, the soil under the seepage area must contain soil air with oxygen. Oxygen is needed for the aerobic bacteria, which eat or break down the biomat on the soil side of the trench or bed. If the soil pores are saturated with water, they cannot contain soil air. No oxygen is present and
