What is a soil restrictive horizon, and why does it matter for drainfield design?

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Multiple Choice

What is a soil restrictive horizon, and why does it matter for drainfield design?

A soil restrictive horizon is a layer in the soil profile with limited permeability that slows or blocks the movement of effluent. Examples include dense clay layers, cemented pans, or bedrock close to the surface. This matters for drainfield design because the drainfield relies on soil to accept and treat effluent as it percolates away from the trench. If a restrictive horizon sits within the zone where effluent would travel, it can impede infiltration, causing perched water, reduced absorption area, and poorer treatment. That means you may need a larger drainfield area or a different design to achieve proper treatment and avoid failures or contamination. Identifying the depth and extent of the restrictive horizon during site assessment is essential for an appropriate, code-compliant design.

A soil restrictive horizon is a layer in the soil profile with limited permeability that slows or blocks the movement of effluent. Examples include dense clay layers, cemented pans, or bedrock close to the surface. This matters for drainfield design because the drainfield relies on soil to accept and treat effluent as it percolates away from the trench. If a restrictive horizon sits within the zone where effluent would travel, it can impede infiltration, causing perched water, reduced absorption area, and poorer treatment. That means you may need a larger drainfield area or a different design to achieve proper treatment and avoid failures or contamination. Identifying the depth and extent of the restrictive horizon during site assessment is essential for an appropriate, code-compliant design.

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