According to WAC, where should mound systems NOT be constructed?

Mound systems are a type of onsite sewage treatment system that requires specific site conditions to function effectively. The construction of mound systems in drainage ways or areas subject to flooding is not advisable because these locations can lead to significant issues with effluent management.

When mound systems are situated in areas prone to flooding, there is a high risk that rising water levels could interfere with the system's ability to properly treat sewage. Flooding can cause the effluent to be pushed back into the mound or even out into the surrounding environment, which can contaminate surface water and groundwater sources. Proper drainage is essential for the mound system to work effectively, as it relies on percolation through the soil to break down waste materials. In areas that are frequently flooded, soil saturation can occur, limiting the treatment capability and potentially leading to system failure.

This principle of positioning mound systems in flood-prone areas underlines the importance of site evaluation and environmental considerations in the installation of septic systems, ensuring they are located where they can function effectively and safely without risk of inundation.