The water utilities do that every year. Routine maintenance. They just finished in our area, sent a text message to all customers work completed for this year. Suburb of DC.
Yep.
The flushing route is carefully planned, and valves are opened and closed to control the
direction of the water flow. Flushing the water system on a routine basis removes sediment
from lines and keeps the entire distribution system “refreshed”. As a result of the line flushing
process, residents in the immediate vicinity of the work may experience temporary
discoloration of their water. This discoloration consists primarily of harmless silt and air and
does not affect the safety of the water. If you experience discoloration in your water after
crews have been flushing in your neighborhood, clear the pipes in your own home by running
all water faucets for a minute or two.
https://brunswickmd.gov/vertical/Sites/%7B6128680E-2B73-4AA3-90D8-2ADE82D7827D%7D/uploads/WHY_DOES_THE_CITY_FLUSH_WATER_LINES_AND_FIRE_HYDRANTS.pdf
https://lebanon-utilities.com/2015/10/11/why-do-we-flush-the-hydrants/