What is the only system that may be constructed in soils with a T-time exceeding 50 minutes per centimeter?

What is the only system that may be constructed in soils with a T-time exceeding 50 minutes per centimeter?

• A. Shallow buried trench system
• B. Raised absorption trenches
• C. Conventional septic system
• D. Mound bed

Answer: (A)

When the soil’s T-time is very slow, meaning it takes a long time for water to move through the soil (over 50 minutes per centimeter), the soil’s natural filtration capacity is limited and has to be used carefully. A shallow buried trench system is designed for that situation because it places the absorption area close to the surface and distributes effluent across many short, shallow trenches. This setup makes use of the slow soil more effectively without requiring deep, heavily saturated conditions or extensive engineered fill. Other systems rely on more rapid infiltration or deeper, thicker absorption zones (or raised beds and mounds with special fills), which won’t perform reliably in soils with such slow percolation, so they’re not suitable.

When the soil’s T-time is very slow, meaning it takes a long time for water to move through the soil (over 50 minutes per centimeter), the soil’s natural filtration capacity is limited and has to be used carefully. A shallow buried trench system is designed for that situation because it places the absorption area close to the surface and distributes effluent across many short, shallow trenches. This setup makes use of the slow soil more effectively without requiring deep, heavily saturated conditions or extensive engineered fill. Other systems rely on more rapid infiltration or deeper, thicker absorption zones (or raised beds and mounds with special fills), which won’t perform reliably in soils with such slow percolation, so they’re not suitable.