I would suggest working at the action level at first rather than worrying about Areas of Focus vs. Projects for the building sites. In other words, each of the building sites sound like a Context, ie @BuildingSite1, @BuildingSite2. The Problem 1, Problem 2, etc. sound like the Project Levels. The Area of Focus sounds like it would be somethigng like "Building Sites Oversite". This could also be broken down into "Building Site A Oversite", "Building Site B Oversite" (inserting the actual location into it, for example "Grant Avenue Site Oversite".
But as the first commenter suggested it really is up to what works best for you rather than a rigid set of rules.