Kentucky Division of Water Accepts Comment on Newly-Proposed Water Quality Criteria for Selenium
As reported in the November/December 2012 Environmental Letter, The Kentucky Division of Water (DOW) is in the process of completing its Triennial Review of water quality standards. In February 2013, DOW gave public notice of proposed revised water quality criteria for selenium and agreed to receive public comment on the proposed criteria through March 1, 2013.
Following the initial Triennial Review public comment period in the fall of 2012, DOW had proposed to delete the acute water quality criterion for selenium and retain the existing 5.0 ug/L chronic criterion. However, at that time, DOW indicated it was considering adopting state-specific selenium criteria in light of the fact that the current criteria were considered outdated, and not scientifically sound or defensible. DOW conducted additional research and evaluations since that time and developed the revised acute and chronic criteria.
Under DOW’s new proposal, the acute criterion for selenium would be 258 ug/L for protection of warm water aquatic habitat. The revised acute criterion is based upon the methodology set forth in EPA’s 2004 proposed selenium criterion. It also takes into account the modifying effect of sulfate in the water column on the toxicity of selenate.
With respect to the chronic criterion, DOW’s proposal is primarily based on the chronic toxicity effects on fishes due to dietary uptake of selenium rather than exposure to selenium in aqueous concentrations. A fish tissue-based chronic criterion is considered more reflective of actual potential impacts and was derived for the most sensitive fish species found in Kentucky. The proposed chronic criterion for selenium is 8.6 ug/g based upon whole fish tissue or 19.2 ug/g for fish egg/ovary tissue. DOW has proposed that the existing chronic criterion of 5.0 ug/L in the water column would remain a threshold water column concentration indicator that could trigger evaluation of impact based upon fish tissue sampling and the fish tissue criterion.
The proposed amendments to 401 KAR 10:031 are scheduled to be presented to the Administrative Regulation Review Subcommittee (ARRS) of the Kentucky General Assembly at the April 2013 meeting. The consideration of the standards was deferred until that meeting to provide time for DOW to consider comments. If the standards are adopted, certain implementation issues will still need to be evaluated to ensure the new criteria can be made readily enforceable in KPDES permits. While environmental interest groups opposed the proposed selenium criteria based upon claims that the new standards were too lenient, in a comment letter dated March 1, 2013, EPA did not raise any significant concerns relating to the derivation of the proposed criteria. EPA did, however, indicate it had concerns as to how the standards would be implemented in waters affected by intermittent discharges.
To view a complete PDF of the January/February 2013 issue of the Environmental Letter, click HERE.