Not that I am an archaeologist (did 1 basic archaeology subject at uni), but it seems like they've covered the ruins as they have either finished the dig permanently, or for the season. Normally ruins which aren't important are reburied to preserve them.

Is the site going to be built on? IIRC when they are going to build over an archaeological site they often send a team to find out what they can before the site gets concreted over or destroyed. If the finds are spectacular they may be saved.