Maybe someone from the City of Greensboro will contact me soon with an answer or perhaps they'd like to test the rocks I found? RecycleBill@gmail.com When I learn more I'll update this post.
Update: While I've yet to talk with anyone with the City I think we're okay. What you're seeing in the photo is "rocks" or crystals that form when certain chemicals that the City adds to protect us from an event like what happened in Flint, Michigan, get trapped in the hot water heater for a long period of time. These chemicals, possibly sodium metahexaphoshate and phosphate, react due to their close proximity to the heating element in the hot water heater and form solids.
Thus the reason you should drain and refill your water heater about once a year but never do.
