The U.S. EPA Website is open ...

The U.S. EPA Website is open to all.  The latest standards for Regions and Federal are listed there.

https://www.epa.gov/ground-water-and-drinking-water/national-primary-drinking-water-regulations

Water Quality Standards: Regulations and Resources:

https://www.epa.gov/wqs-tech

Safe Drinking Water Act (SDWA)

https://www.epa.gov/sdwa

Regulations Currently in Force:

https://www.govinfo.gov/app/collection/cfr/2019/title40/chapterI/subchapterD/part141

Printable version: Complete NPDWR Table  (attached)