When must special care be given in the design of mounds according to the slope?

In septic system design, special care is particularly critical for slopes greater than 20%. At this steep angle, the potential for erosion and runoff increases significantly, which can lead to several issues for wastewater management. The effectiveness of a mound system relies on the controlled absorption and treatment of effluent through the soil. On steep slopes, water can rapidly travel downhill, reducing the time soil has to adequately filter contaminants before they reach groundwater or surface water.

Additionally, steep slopes can make installation more challenging and may affect the stability of the system, increasing the risk of system failure or environmental contamination. Thus, extra considerations for design, material selection, and placement are necessary to ensure that the mound system operates effectively in these conditions.

While slopes of 10% or less and those between 10% and 20% do require attention, the most stringent precautions are warranted on slopes greater than 20% due to the heightened risk factors involved.