True or False: Leaving lateral trenches uncovered and exposed to rainfall will not harm their intended purpose.

Leaving lateral trenches uncovered and exposed to rainfall is indeed harmful to their intended purpose. Lateral trenches, which are a part of a septic system, are designed to effectively treat and disperse effluent into the ground. When these trenches are exposed to rainwater, several issues can arise.

Rainfall adds excess water to the system, which can saturate the soil and lead to oversaturation. This prevents the effluent from properly draining and can lead to backups and malfunctions in the system. Additionally, unfiltered rainwater can carry contaminants and sediments into the trenches, which could impair the operation of the drainage field and hinder the natural biological processes that break down wastewater.

Furthermore, if the trenches are filled with water from rain, it could result in the effluent being pushed back into the tank rather than being absorbed by the soil. This situation can lead to a rise in system failure risks and potentially create environmental hazards.

In contrast, the other options suggest varying degrees of harm depending on conditions or assumptions, but any exposure to rainfall without proper cover typically has negative consequences for the functionality and reliability of the septic system.