Thanks for reporting. I have referred this issue to our Parks and Recreation Department staff. When they have responded I will update this issue.

These are actually likely adrenid bees, a ground-nesting type that emerge from their nests in the spring and generally migrate elsewhere. Sometimes infestations last for a year or two but the good news is that this type of bee does not have a beesnest per se, and nothing to "defend" and so stings from this type of bee are very rare. It is a natural part of the ecosystem around Raleigh and generally nothing to worry about.