Which of the following is a criteria to determine if a subsurface OSSF system is functioning properly?

To determine if a subsurface On-Site Sewage Facility (OSSF) system is functioning properly, one key criterion is that the plumbing system must drain effectively. This indicates that the system is capable of transporting wastewater from the residence or facility to the treatment area without obstruction or backup. Proper drainage is essential for the overall function of the OSSF, as it ensures that the wastewater enters the treatment process efficiently and is not sitting stagnant, which could lead to system failure or other environmental issues.

The other options present conditions that indicate malfunction or failure of the system. For instance, if water is pooling above ground, it signifies that the system is overwhelmed or unable to properly absorb or treat the effluent, leading to potential health hazards and environmental contamination. The presence of foul odors generally indicates that there is a problem within the system, such as inadequate treatment of sewage or overflow, posing a risk to both health and the surrounding environment. Lastly, stating that wastewater must receive no treatment contradicts the fundamental purpose of an OSSF, which is to treat wastewater before it is released into the environment. Effective treatment is critical for preventing pollution and protecting public health.