Water Quality: Docket No. 58-0102-1802

This rulemaking has been initiated to make certain revisions identified as high priority in the 2017 Triennial Review of Idaho Water Quality Standards and to comply with federal requirements for consideration of EPA recommended (aka §304(a)) criteria (40 CFR 131.20): (1) Adopt aquatic life criteria for acrolein, carbaryl, and diazinon in accordance with EPA’s current §304(a) recommended criteria, and (2) adopt EPA’s current §304(a) recommended criteria for bacteria and clarify the definition of recreational use. 

EPA’s Recommended §304(a) Aquatic life Criteria for Acrolein, Carbaryl, and Diazinon

This rulemaking adds criteria for acrolein, carbaryl, and diazinon in Subsection 210.01. Currently, Idaho does not have aquatic life criteria for acrolein, carbaryl, and diazinon, although EPA has issued new recommended aquatic life criteria for these toxics. Acrolein is an aquatic herbicide and is known to be toxic to aquatic life, particularly amphibians and fish. In 2009, EPA added acrolein to the §304(a) list of aquatic life criteria. Carbaryl and diazinon are pesticides that are toxic to aquatic life, particularly invertebrates. EPA added diazinon to the §304(a) list of aquatic life criteria in 2005 and added carbaryl in 2012.

In order to avoid EPA promulgating federal standards for acrolein, carbaryl, and diazinon for Idaho, DEQ proposes to undertake a negotiated rulemaking to revise these aquatic life criteria in Idaho’s water quality standards. By adopting these criteria, DEQ will comply with federal requirements for consideration of EPA recommended criteria (40 CFR 131.20) and ensure that its criteria provide sufficient protection of aquatic life uses.

EPA’s §304(a) Recommended Criteria for Bacteria

This rulemaking adopts EPA’s 2012 §304(a) recommended criteria for bacteria. EPA’s 2012 §304(a) criteria includes both E. coli criteria as well as enterococci criteria; either of which would be considered protective of contact recreation. States (and dischargers) can use either criterion to demonstrate compliance with water quality standards. This rulemaking also clarifies the definition of recreational use, recognizing that waters designated for primary contact recreation (PCR) also include recreational activities associated with secondary contact recreation (SCR).

Consideration of enterococci criteria as included in EPA’s 2012 §304(a) recommendation is necessary to comply with federal requirements for consideration of EPA recommended criteria (40 CFR 131.20). Enterococci criteria are more directly related to incidences of gastrointestinal illnesses than E. coli criteria. In addition, rapid analytical techniques for enterococci are currently being developed. By adopting enterococci criteria, Idaho will be in a position to easily integrate any advances to improve sampling logistics (for example, extended holding times and field preservation to allow for monitoring and assessment of more remote waters, and rapid notification of affected swimming beaches and recreational facilities).

DEQ will also consider the adoption of statistical threshold values (STV) as criteria. The STV is a concentration that is not to be exceeded more frequently than 10% of valid samples collected in a 30-day period.

By adopting EPA’s 2012 §304(a) criteria recommendation, DEQ can meet a recommendation of the 2017 Triennial Review and meet federal requirements to consider EPA’s 2012 §304(a) recommendations while providing the same level of protection for Idaho water bodies. In addition, this allows dischargers the option to request an alternative fecal indicator bacteria for monitoring compliance with water quality standards.