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Water Quality Standards Revisions for Freshwater Ammonia​ 2014


DEQ is initiating a rulemaking to address EPA’s Jan. 31, 2013 disapproval of ammonia criteria that DEQ adopted in 2004. Oregon’s adopted criteria were based on EPA’s 1999 recommended criteria, which did not take into consideration ammonia toxicity to certain kinds of freshwater mussels and snails. EPA has since updated its national recommendation for ammonia in response to new mussel and snail sensitivity data, and published final revised criteria in the Federal Register on August 12, 2013. As part of the rulemaking, DEQ is also proposing to correct an error to the basin-specific criterion for pH for the main stem Snake River, which DEQ inadvertently limited to a portion of the basin during a rule update in 2003. In addition, DEQ is proposing to correct or clarify portions of water quality standards that have been recently disapproved by EPA.


Until Oregon adopts revised criteria for ammonia and EPA approves those revisions, Oregon’s currently effective ammonia criteria are based on EPA recommendations from 1985 (criteria last approved by EPA). These criteria are in Table 30 and can be derived based on pH and temperature using the ammonia calculator located on the toxics website.

At this time, DEQ anticipates adopting revised ammonia criteria to protect freshwater aquatic life based on EPA’s August 2013 recommendations, including the assumption that unionid mussels and non-pulmonate (gill bearing) snails are present in Oregon freshwater systems. EPA’s criteria are expressed as Total Ammonia Nitrogen (TAN) and are derived based on the pH and temperature of the water. See EPA’s website for more information about its ammonia recommendations.

The proposed rule would correct an error made in 2003 for the basin-specific pH standard for the main stem Snake River. The current standard incorrectly applies the standard to river miles 260-335 of the Snake River. This rule revision would correct that error so to ensure that the pH standard applies throughout the main stem Snake River in Oregon. DEQ also is proposing to make clarifying comments, noting that the statewide narrative natural conditions criterion at OAR 340-041-0007(2) and numeric natural conditions criterion under the temperature standard were disapproved by EPA as a result of a court decision. Finally, DEQ is proposing to correct basin-specific standards for the Umatilla Basin so that they reflect EPA’s partial disapproval of DEQ’s revisions to the basin-specific standards that were adopted in 2012.

Prior to initiating this rulemaking, DEQ met with a number of stakeholder groups to discuss EPA’s latest ammonia recommendations and its potential application to Oregon waterbodies. Feedback received indicated that generally, EPA’s recommendations are appropriate for Oregon and that DEQ should move forward quickly to adopt such revisions. Given this input, DEQ is not forming an advisory committee for this rulemaking. Members of the public will have an opportunity to provide comments on the rulemaking as part of the public comment process. See anticipated rulemaking schedule below:


Ammonia Rulemaking Schedule - Milestone and Estimated Timeframe

Initiate rulemaking .... April 2014

Public comment and hearings ..... October 2014

Environmental Quality Commission adoption ..... January 2015

EPA action ..... May 2015



Stay informed about the ammonia rulemaking by clicking the green envelope at the top left corner of this page to be added to DEQ’s mailing list for water quality standards rulemaking. Information related to the ammonia rulemaking will also be added to this website as it becomes available.