What should be ensured about the drainage system before the new drainage installation is complete?

The correct answer emphasizes the importance of a fully functional drainage system as a critical aspect of the installation process. Ensuring that the drainage system is fully operational before the installation is complete is essential for several reasons. A functional drainage system prevents water accumulation, directs stormwater properly, and reduces the risk of flooding or erosion in the surrounding areas. If the drainage system is non-functional during or after the installation process, it can lead to costly repairs, safety hazards, and compliance issues with local regulations.

Having a fully operational drainage system also allows for immediate testing and assessment of the installed components, ensuring that they work as intended and meet engineering standards. Identifying any issues at this stage is crucial as it enables timely corrective actions, thereby maintaining project schedules and budgets.

The other options highlight points that do not align with best practices in drainage installation. For instance, the idea that the drainage system must be entirely replaced is unnecessary if the current system is functioning properly. Stating that the system must remain inactive contradicts the goal of ensuring it is operational. While inspection by local authorities is important, it typically occurs after the installation process, making it less critical than having the system fully functional during installation.