What is required for soil with an absorption rate exceeding 60 minutes per inch?

For soil with an absorption rate exceeding 60 minutes per inch, the use of gravel backfill with Low-Density Gravel Pits (LDGP) systems is required. This is important because soils that have a slow absorption rate are less effective in handling wastewater, which can lead to potential environmental issues if they are not properly managed.

The incorporation of gravel backfill helps improve the drainage and aeration of the soil in these systems, allowing for more effective absorption and treatment of effluent. Gravel creates a medium that facilitates better flow and distribution of wastewater, mitigating the risks associated with slow-draining soils. This is crucial for maintaining the proper functioning of the septic system and ensuring environmental safety.

The other choices do not satisfy the need for optimizing effluent absorption in slow-percolating soils, which is why they do not align with the established requirements for septic system installations in Tennessee.