Which of the following best defines an Existing System in wastewater management?

An Existing System in wastewater management refers specifically to an onsite wastewater system that has received final construction approval. This definition emphasizes that the system has successfully gone through the necessary regulatory processes and has been deemed compliant with applicable codes and standards. Final approval indicates that all construction has been completed to the specifications required by local authorities, ensuring that the system is operational and meets health and environmental guidelines.

In contrast, the other options do not reflect the concept of an existing system accurately. A new wastewater system being constructed would still be in the process of being built and has not yet received approval or been operational. A system that has not been approved by regulatory agencies implies that it is in a state of non-compliance or requires further examination before it can be used. Lastly, a wastewater system based solely on verbal approval lacks formal verification through documented processes, which is essential for ensuring safety and regulatory compliance. Therefore, final construction approval is crucial in defining an existing system.