What is the purpose of a leach field?

The purpose of a leach field, also known as a drainage field or soil absorption field, is to distribute effluent from a septic tank and filter it through the surrounding soil. This process is crucial for treating the wastewater before it returns to the groundwater or surface water systems. When the effluent exits the septic tank, it is piped into the leach field where it seeps into the soil. The soil acts as a natural filter, breaking down organic matter and bacteria present in the effluent through biological processes. This filtration not only cleans the water but also helps recharge the groundwater supply.

In contrast, the other choices imply different functions that are not associated with a leach field. For example, the collection and storage of solid waste is primarily the function of the septic tank itself, not the leach field. While there can be a variety of systems aimed at flood control, creating a barrier against flood water is not a role of the leach field. Additionally, separating drain water from sewage is a specific action related to plumbing design and tank functions, not the distribution of effluent for soil absorption in a leach field.