The Freshwater For Life Coalition, or FLAC, delivered a letter to Barrett on Tuesday.
The group is demanding the city take big, immediate steps to address its crisis of lead pipes carrying water into thousands of homes.
The call comes after news erupted late last week during a Water Quality Task Force meeting. Its members learned Milwaukee did not mandate the use of copper pipes until 1962. For months, city leaders had been repeating the message that only people living in homes built prior to 1951 likely had lead service lines.