Ash ponds are managed so that the solids in the water drop out of solution, collecting or settling in the pond, effectively preventing airborne particles. The clear surface water discharged from Ameren ash ponds is subject to federal National Pollution Discharge Elimination System (NPDES) limitations. These limitations take into consideration both the national technology-based treatment standards for ash ponds and local water quality standards.

This means that at our generating facilities permits require routine monitoring and establish limitations for parameters, such as total suspended solids and corrosivity.