How far must down-gradient cuts with less than 5 ft. of soil above a restrictive layer be set back from the edge of a drain field?

The correct distance for down-gradient cuts with less than 5 feet of soil above a restrictive layer to be set back from the edge of a drain field is 25 feet. This setback distance is critical because restrictive layers, such as clay, bedrock, or other impervious materials, can impede the movement of wastewater and affect the performance of the septic system.

By maintaining a setback of 25 feet, it ensures that any potential downslope water movement does not directly interfere with the drain field's operation. The distance allows for adequate filtration and absorption capacity of the soil to treat wastewater effectively before it reaches any restrictive layer, thus preventing contamination of groundwater and maintaining the effectiveness of the septic system. This regulation is in place to safeguard both public health and environmental quality.