The U.S. EPA released a memo yesterday stating that insufficient monitoring methods and nascent environmental data exists – therefore will not regulate OA under CWA 303(d) and will not be establishing TMDL’s at this time. Due to
seasonal and regional fluctuations in pH, the EPA has determined that most states have insufficient data to find that OA is impairing their water bodies. States are encouraged to continue research in OA to learn about
this problem, and specifically to study already impaired or sensitive waters. States are also encouraged to list their own imparied waters for pH under existing regulation (6.5 – 8.5, +0.2 natural varialtion) and to list
OA as the source if enough data has been collected to reflect this. Lastly, EPA stated that they will provide guidance as assessment methods of OA improve.