Digger Bees

Walking the dogs at one of the local parks I frequent. I came across this in the lawn (see below).  

These are digger bees coming out of the ground. Digger bees are solitary bees and are not to be confused with hives of ground wasps aka "ground bees" that I have gotten into several times when digging on the dogs, not are they Cicada Killer Wasps whose larva, the Velvet Ant, packs a nasty wallop. 

Digger bees dig little dirt pipes and stock each underground cell with pollen and nectar, and then deposit their eggs on the food mass. When the egg hatches, the bee larva consumes the pollen and nectar, pupates, and then becomes an adult bee emerging in the spring. Adult bees will overwinter below ground at the burrow site. 

I suspect this location is popular because the soil is soft and a bit sandy.  I wonder if all of these young bees represents the work of just one mamma bee?