How does seasonal thaw impact existing mound systems?

The impact of seasonal thaw on existing mound systems is predominantly related to changes in soil conditions and groundwater levels. During thawing periods, moisture levels in the soil can rise significantly due to the melting of snow and ice. This increase in moisture can lead to heightened effluent flow from the mound system.

As the ground becomes saturated with water, the system may struggle to effectively absorb additional wastewater, leading to potential oversaturation. When the soil is oversaturated, it can result in reduced treatment efficiency and possibly cause system failures, including surface runoff or effluent surfacing, which are signs that the system is overwhelmed.

In contrast, the other options do not accurately describe the primary effects of seasonal thaw. Increased plant growth may occur due to better moisture availability, but this is not a direct impact on the mound system itself. Saying that the thaw has no significant impact overlooks the pronounced effects of saturation. Lastly, a decrease in the absorption rate is not correct; rather, the absorption capacity can be compromised due to saturation conditions instead of a general decrease. Therefore, the correct understanding is that seasonal thaw can lead to increased effluent flow and potential oversaturation, which poses risks to the functioning of mound systems.