Total Maximum Daily Loads

The Oregon Department of Environmental Quality will convene an advisory committee beginning December 2017, for developing a revised Willamette Basin Mercury TMDL.


In September 2006, EPA approved DEQ’s mercury TMDL for the entire Willamette Basin. DEQ developed the TMDL to meet a mercury criterion in place at the time. Northwest Environmental Advocates filed a lawsuit in 2012, which argued the validity of the mercury  TMDL and EPA’s approval of the TMDL. In April 2017, the US District Court issued a ruling requiring EPA to revise the TMDL by April 2019, and allowing the 2006 TMDL to remain in effect until EPA issues or approves the revised TMDL.
DEQ and EPA are revising the TMDL to meet Oregon’s current water quality criterion for methylmercury, which is eight times more stringent than the criterion in effect in 2006. EPA approved Oregon’s revisions to its methylmercury fish tissue concentration criterion for the protection of human health in October 2011. The revised criterion changed the acceptable level from 0.3 mg/kg (milligram of methylmercury per kilogram of fish tissue) to a significantly more protective 0.040 mg/kg.

Committee documents


Meeting materials

Agenda - Dec. 5, 2017


Willamette Basin Mercury TMDL Project Coordinator:
Paula Calvert, 503-229-5101