What is the name of the formation that may cause soil clogging?

• A. Biomat
• B. Groundwater plume
• C. Mottling
• D. Calcification

Answer: (A)

A biomat is the biologically active layer that can form at the infiltrative surface of a soil absorption field. As wastewater reaches the soil, bacteria and other microbes, along with decomposing organic matter, produce extracellular substances that create a slimy, gel-like mat. This mat coats soil particles and fills pore spaces, dramatically reducing the soil’s ability to absorb water. Over time, the biomat can slow or halt effluent movement, leading to soil clogging and potential drain-field failure. The other options refer to different soil phenomena: a groundwater plume involves contaminants moving through groundwater, mottling is irregular soil coloring from redox changes, and calcification is mineral deposition forming hard layers. None of those form the clogging layer at the infiltration surface like a biomat.