20-50 bees were cruising around a small (1m2) area of open soil. Females were often landing and investigating crevices. Couldn't tell if they were emerging or aiming to dig. Many males as well (see second image, with moustache), and often tackled females, though it didn't seem that they were ever successful in mating (no photos revealed even correct orientation, let alone visible genitalia). Keyed using pinned specimens, and got confirmation from bugguide-ascher
Saw several of these guys crossing the road as Dave B. pointed them out.
On Sand Run Parkway at Summit Metro Parks program