The clogging mat, or 'biomat', is an important element of your septic system that builds naturally under your drainlines. The mat is a complex formation of microorganisms that provides some treatment, effectively slows the movement of liquid into the soil, and can help keep the soil beneath it from becoming saturated. Unsaturated soils below your drainfield trenches allow wastewater to slowly pass downward through the soil with sufficient time for the soil bacteria and natural die-off to remove all pathogens of human health concern. If the soils beneath your drainfield are saturated, they can't handle and treat the effluent being distributed by your drainfield pipes. In essence, you will not be sure that the wastewater will be free of disease-causing organisms or other nutrients harmful to the environment.
Effluent distributed into the soil eventually ends up in the groundwater.
A simple drainfield relies on gravity to distribute the clarified effluent over the soils. Every time water enters the septic tank, water leaves the septic tank for the drainfield. In a gravity system the drainfield gets liquid whenever we use water in the house. Make sure your drainfield isn't overloaded by excess water drained from roof tops, hot tubs or anything else under your control. Keep any irrigation system at least 10 feet from the edge of your septic system.