Water Effect Ratio Studies
EA assists clients with the development of site-specific water quality criteria for individual metals through the
performance of water effect ratio (WER) testing. This type of study enables clients to modify National Pollutant
Discharge Elimination System (NPDES) discharge permit single metal permit limits. This testing is based on the U.S.
Environmental Protection Agency (EPA’s) recognition that the metals can be substantially less toxic in an effluent/receiving
water matrix than in clean laboratory water, on which single metal permit limits are based.
EA assists clients with the following permit modification procedures:
- EPA Water Effect Ratio
- EPA Recalculation Procedure
- EPA Resident Species Procedure.