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Impaired Waters and TMDLs

Willamette Basin Mercury TMDL

On December 30, 2019, EPA established the Willamette Basin Mercury TMDL. Minor changes were made to the TMDL after reviewing comments received during the public comment period, and EPA reissued the TMDL on February 4, 2021. A copy of the final TMDL and related documents are provided below, including a summary of the revisions.

EPA’s TMDL incorporates much of Oregon’s 2019 TMDL, with the major changes being revisions of some of the load and wasteload allocations to ensure that the TMDL meets the mercury water quality standards.

Questions? Contact Alan Henning (, 541-687-7360, or Cami Grandinetti (, 206-553-8696.

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