What is the procedure that places a manhole under a vacuum to test the structural integrity of the manhole?

The correct answer is vacuum testing, which is a procedure specifically designed to evaluate the structural integrity of a manhole. During this process, a vacuum is created inside the manhole, allowing for the detection of potential leaks or weak spots. By subjecting the manhole to a lower pressure, it is possible to observe any deformation or failure in the structure, ensuring that it can withstand environmental conditions and operational stresses.

Vacuum testing is particularly advantageous because it offers a thorough assessment of manhole integrity without the need for significant water usage, as is typical in hydro testing. It is also effective in identifying defects that may not be apparent during visual inspections or other testing methods. This procedure allows for early detection of issues that could lead to groundwater infiltration or surface contamination, essential for maintaining the reliability and safety of the collection system.

Other testing methods, such as hydro testing or pressure testing, serve different purposes and may not be suitable for assessing a manhole's structural integrity in the same effective manner. Leak testing tends to focus more on identifying leaks rather than assessing the overall structural stability. Thus, vacuum testing emerges as the most suitable and effective method for the specific task of testing a manhole's structural integrity.