What percentage of gravel in soil is acceptable for drainfield if gravel is greater than 2mm?

The ideal percentage of gravel in soil for a drainfield, when considering gravel greater than 2mm, is less than 30%. This is because a significant amount of gravel can lead to drainage issues, as it can create large voids that may not hold moisture effectively, affecting the soil's ability to biofilter and treat wastewater properly.

Soil with too high a concentration of gravel may not provide the necessary contact and interaction between the effluent and the soil particles, which is crucial for the natural treatment process. By keeping the gravel percentage below 30%, the soil retains more finer particles that contribute to better water retention and filtration, enabling the drainfield to function effectively in treating on-site wastewater.

Understanding the role of different soil components in the drainage field is critical for ensuring proper functioning and compliance with OSSF regulations.