Which component is commonly used to elevate the drainfield in high groundwater situations?

• A. Absorption trenches
• B. Mound system
• C. Standard bed
• D. Surface irrigation

Answer: (B)

When groundwater is high, you need to create space between the drainfield and the water table while still providing effective treatment. A mound system accomplishes this by building a raised bed of engineered fill (often sand) on top of the native soil and placing the distribution lines within that mound. The effluent moves through the fill media and then into the soil at a higher elevation, which maintains proper separation from the groundwater and improves infiltration and treatment.

Absorption trenches and a standard bed sit at or near grade and rely on the native soil conditions, so they don’t raise the drainfield. Surface irrigation distributes effluent at or near the surface and isn’t used to elevate the disposal field.