What causes a city to issue a boil water notice?

AUSTIN (KXAN) — After Austin Water announced a citywide boil water notice late Saturday, city officials stressed there was no indication of contamination in Austin's water supply. But what leads to issuing a boil water notice in the first place?What leads to a boil water notice?In this latest example in Austin, the citywide notice was due to high turbidity, or cloudiness, in the city's water system. High turbidity is one of two key violations outlined by the Texas Commission on Environment