According to specific design criteria, a manhole can be installed within 9 feet of an existing waterline if it is:

A manhole can be installed within 9 feet of an existing waterline if it is completely watertight and has been tested for leakage. The reason for this design criterion is primarily focused on preventing contamination of the water supply. When a manhole is watertight, it ensures that any wastewater or contaminants within the sewer system cannot seep out into the surrounding soil or groundwater, which could potentially reach the nearby waterline. Testing for leakage signifies that the construction and materials of the manhole have met the necessary standards to maintain this integrity.

This standard prioritizes public health and environmental safety by minimizing the risk of cross-contamination between wastewater systems and potable water sources. The other options do not provide the necessary assurance that contamination will be controlled in close proximity to a drinking water supply.