In terms of OSS, what is a "well" used for?

A "well" in the context of On-Site Sewage Systems (OSS) is primarily utilized for monitoring the depth to a water table. This function is critical because understanding the water table's depth helps in determining the appropriate design and placement of septic systems. It ensures that the system functions effectively without contaminating groundwater or causing environmental harm, as the water table's proximity can affect the ability of the soil to adequately treat effluent.

Knowing the depth to the water table allows installers to assess the soil's capacity for drainage and treatment of wastewater, ensuring compliance with health regulations and safeguarding public health. In contrast, the other choices do not accurately reflect the primary use of a well in this scenario. Testing soil quality typically involves boreholes or test pits, while dispersing treated water is a function of the leach field. Providing drinking water, although a function of some wells, does not align with the specific context of OSS systems where the depth to the water table is of paramount concern.