Following a public comment period from July 3, 2019 to Sept. 6, 2019, DEQ issued the Revised Willamette Basin Mercury TMDL on Nov. 22, 2019. The updated TMDL built upon the original TMDL modeling analysis and made substantial improvements.
On Nov. 29, 2019, EPA disapproved the TMDL after determining that the load and waste load allocations based on percent reductions would not achieve the TMDL target in all the subbasins addressed by the TMDL. Under the Clean Water Act and implementing federal regulations, EPA established a new TMDL on Dec. 30, 2019, which became effective for Clean Water Act purposes. EPA's TMDL incorporated some of Oregon's 2019 TMDL with the major changes being revisions of some of the load and wasteload allocations.
EPA accepted public comments on the Dec. 30, 2019 TMDL from Jan. 6, 2020 through Feb. 4, 2020, and revised the TMDL in response to comments received. EPA issued the final TMDL on Feb. 4, 2021. EPA's TMDL (EPA's 2019 TMDL, as revised to address public comments received in 2020) incorporates by reference those sections of DEQ's 2019 TMDL that EPA found to be consistent with the Clean Water Act and EPA's requirements.