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Technical Memo  Page 5 August 16, 2024 <br />Peabody – CDPS Permit Supplement <br />Criterion emphasizes that egg-ovary samples collected during the spawning period can be <br />highly variable depending upon the ripeness of the eggs. Therefore, the few samples that <br />have both a whole-body and egg/ovary component (i.e., samples analyzed as whole-body <br />minus eggs) are not included in the mean whole-body calculations in Table A-1. Due to the <br />relatively limited size of the dataset for egg-ovary samples, we utilize the mean whole-body <br />results by species as this provides a better tracking of selenium in tissues over time. <br />3.Regulatory Updates <br />The EPA’s 2016 Criterion was originally released with draft TSDs to assist entities in the <br />implementation of the 2016 Criterion, these drafts were later withdrawn. Revised draft TSDs <br />were then released for public comment in October 2021 (EPA 2021a – d). In April 2024, <br />final TSDs were issued consisting of the following: <br />•Technical Support for Adopting and Implementing EPA’s 2016 Selenium Criterion in <br />Water Quality Standards (EPA 820-R-24-001; EPA 2024a) <br />•Technical Support for Fish Tissue Monitoring for Implementing the EPA’s 2016 <br />Selenium Criterion (EPA 820-R-24-003; EPA 2024b) <br />•Frequently Asked Questions: Implementing Water Quality Standards Based on EPA’s <br />2016 Recommended Selenium Criterion in Clean Water Act Sections 402 National <br />Pollutant Discharge Elimination System Permits (EPA 820-R-24-002; EPA 2024c) <br />•Frequently Asked Questions: Implementing EPA’s 2016 Selenium Criterion in Clean <br />Water Act Sections 303(d) and 305(b) Assessment, Listing, and Total Maximum Daily <br />Load Programs (EPA 820-R-24-004; EPA 2024d) <br />As a result of the release of final TSDs in April 2024, the following supplemental <br />information is being submitted by Peabody for consideration by CDPHE as renewal permits <br />are finalized. Specifically, this information is being evaluated as it relates to the clarifications <br />and direction provided by EPA 2024c for the use of selenium concentrations in fish tissue for <br />conducting RP analysis. <br />3.1 Primacy Given to Fish Tissue <br />Both the 2016 Criterion and 2024 final TSDs recommend that primacy be given to fish <br />tissue, when available, as the criterion utilized to protect aquatic life. In footnote 6 of A1-2 in <br />EPA 2024c, the primacy of tissue elements over water column elements is confirmed. <br />Implementation methods for tissue-based selenium limits within discharge permits is largely <br />left to states and tribal entities based on site-specific conditions.