Which of the following would be classified as a non-transient, non-community water system (NTNCWS)?

A non-transient, non-community water system (NTNCWS) is a type of public water system that provides water for human consumption to at least 25 of the same people over six months a year, but is not used primarily for residential purposes.

In this context, the water supply serving a factory with at least 25 employees qualifies as an NTNCWS because it consistently serves the same group of individuals—namely, the employees of the factory. This meets the criteria of having a stable population that is not transient, given that these employees typically work at the factory on a regular basis.

In contrast, a water supply serving a campground generally caters to a fluctuating number of visitors, which would classify it as a transient system. A water supply serving a small city would fall under a community water system, serving permanent residential users. Similarly, a water supply to a highway rest area also serves a transient population, as the users are temporary travelers and do not form a stable group over time. Hence, these scenarios do not meet the specific criteria set for NTNCWS classification.