How many angels can dance on the head of a pin?

... I don't know the answer to that, but there seem to be about 40 people working on this playground construction site.

Based on the slideshow, there seems to be a multitude of tasks for the volunteers - painting murals, making a new sidewalk, and so forth - so it's likely that the crew didn't reach the point of diminishing returns (i.e., the too-many-cooks-spoil-the-broth syndrome). But back in my playground construction days the magic number for a crew was 4 or 5: any more, and there would be at least one person loafing at all times; any fewer, and the job would take ages.