Recommendations to EPA Region 3 states when developing sampling plans for calculating a site-specific freshwater copper criterion using the biotic ligand model (BLM). These recommendations are based on existing EPA guidance and do not contain or constitute any new EPA policy. EPA recommends that the state submit the study plan for a site-specific criterion to EPA for comment prior to implementation. Region 3 has consolidated existing guidance on the copper BLM into this document to assist the Region 3 states in ongoing efforts to implement the copper BLM. This guidance may be updated as EPA evaluates the nationwide implementation of the copper BLM.You may need a PDF reader to view some of the files on this page. See EPA’s About PDF page to learn more.