You didn't say how many users or how many construction sites or what the relationship between them is.
Your choice of solution should take into consideration that Moodle assumes many students with respect to a course.
Some other ideas:
- Use one Moodle course, but make a copy of the same quiz for each construction site. All users are enrolled in the Moodle course, but don't have to take all the quizzes. They will see them when they log in, however.
- Make a Parent course that has the standardized quiz, but create a child course for each construction site. You can enroll users in each child (construction site) course and they'll only see the one quiz. You can also override the deadlines for that quiz for each construction site.