What might be the cause of a failing lateral line in a shallow gravel trench system?

A failing lateral line in a shallow gravel trench system can occur due to various factors that disrupt its functionality. In this case, a shift in the distribution box is a significant cause of failure. The distribution box is responsible for evenly distributing effluent from the septic tank to the lateral lines. If it shifts, the distribution of wastewater can become unbalanced, leading to areas of the lateral line being over-saturated while others may not receive enough effluent. This can result in backup and ultimately failure of the lateral lines.

In contrast, while tree root accumulation, improper soil type, and heavy rainfall can all negatively impact the performance of a septic system, they are not specifically related to the immediate function of the distribution box like the shift is. Tree roots may invade lines and cause blockages, improper soil can inhibit drainage, and heavy rainfall can lead to inundated systems, but these situations do not directly concern the operational integrity that stems from the position and function of the distribution box.