Kentucky’s Receives EPA’s Final Decision on Water Quality Standards

Kentucky has received EPA’s final decision  in response to the May 2013 revisions to Kentucky’s water quality standards done as a part of the Triennial Review of our water quality regulations. EPA has approved all changes made to Kentucky’s water quality standards with the exception of one item.

Details on Kentucky’s revision to its water quality standards can be found at this website:

Of particular note, the agency is pleased that EPA has approved Kentucky’s science with respect to the Kentucky specific chronic water quality criteria for selenium. This approval by EPA affirms Kentucky’s review and evaluation of the science that has developed and evolved over the course of the last several years that diet is the primary pathway of selenium exposure for aquatic life. Chronic water quality criteria serve the purpose of protecting aquatic life against potential long-term impacts of a pollutant such as lethality, reproduction, developmental or related potential long-term effects.  As such, chronic water quality criteria are an integral component of water quality standards for the protection of aquatic life through maintaining water quality nationally and in Kentucky.

EPA also disapproved the proposed revision to the acute water quality criteria for selenium.  Acute water quality criteria serve the purpose of protecting against potential short-term impacts of a pollutant, typically lethality. While EPA states that acute toxicity rarely occurs in the aquatic environment, even at high selenium levels in the water column, EPA bases its disapproval of Kentucky’s proposed acute water quality criteria for selenium on chronic endpoints (impacts accrued through  dietary ingestion) rather than acute endpoints (lethality). This denial therefore is a departure from how EPA has previously developed acute water quality criteria for pollutants regulated under the Clean Water Act.

In light of the disapproval of the acute water quality criterion, the practical result of EPA’s action is that Kentucky’s previous acute water quality criterion of 20 ug/l will continue to serve as the acute criterion for purposes of implementing the Clean Water Act in Kentucky. Any changes to the previous acute criterion of 20 ug/l would have to undergo a future regulation change by Kentucky and subsequent approval by EPA.

Pursuant to federal EPA regulations, 40 CFR 131.21(a)(2), a disapproval by EPA shall specify the changes needed to assure compliance with the requirements of the Act and this regulation, and shall explain why the State standard is not in compliance with such requirements. In disapproving the acute criterion, EPA did not indicate what an acceptable acute criterion should be or whether an acute criterion is even necessary in light of EPA’s disapproval of the acute criterion predicated on chronic concerns, while  approving  Kentucky’s chronic water quality criteria for selenium which address those chronic concerns expressed by EPA. Several states do not have an acute water quality criterion for selenium.

EPA has indicated its intentions to pursue promulgation of national water quality criteria for selenium in the coming months. The national water quality criteria for selenium have not been updated in several years.

In summary, Kentucky is pleased by EPA’s approval of Kentucky’s revisions to its water quality criteria affirming Kentucky’s science-based review of its water quality criteria during this Triennial Review.

For more information on Kentucky’s Water Quality Standards, contact Randy Payne at or 502-564-3410, ext. 4856.