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Technical Memo  Page 3 August 16, 2024 <br />Peabody – CDPS Permit Supplement <br />concentrations in fish tissue, removing the need for a water column value to be included <br />within the permit. <br />Fish populations within the study drainages are restricted to the lower portions of each <br />drainage, as flows limit the ability of fish to navigate and persist within the upper portions of <br />each drainage. Therefore, fish data presented in Table A-1 (Attachment A) include results <br />from the first point downstream of the outfall that has habitat to support fish populations. <br />2.1 Overview of Data Collected to Support Selenium Study <br />Habitat and biological samples have been collected throughout the study area since 2012. <br />Data collection at study sites have included the following elements: <br />•Habitat assessments, combined with additional substrate quality evaluations <br />Measurements of bank and wetted width, water depths, substrate <br />composition, and bank structure have been collected at each site across <br />multiple years. Habitat assessments were modified in 2023, and only <br />wetted width and site length data were collected from each site. <br />•Quantitative fish population sampling at each site with sufficient flows <br />All fish measured for length and weight: <br />o Used to determine which species are reproducing in the watershed <br />or if fish populations are sustained by immigration into the study <br />reach. <br />All fish examined for selenium-related deformities and other DELTs (i.e., <br />fish deformities, erosions, lesions, and tumors). <br />Fish population density, biomass, and condition factors used to assess fish <br />community structure and condition. <br />•Evaluation of selenium concentrations in aquatic life and periphyton/sediment as <br />measured in the laboratory in the following matrices <br />Whole-body fish tissues (from multiple trophic levels, when available) <br />o Typically, samples not composited, except few instances to <br />collect sufficient sample mass (e.g., Brook Stickleback, <br />Fathead Minnow, Redside Shiner) <br />Fish egg/ovary (E/O) tissue samples collected, when available <br />Macroinvertebrate tissues: <br />o Collected only at sites with fish from 2012 – 2021. <br />o Collected at all sites where sufficient water was present, 2022 <br />- 2024. <br />Periphyton and sediment samples collected in most years: <br />o Collected only at sites with fish from 2012 – 2021. <br />o Collected at all sites when available, 2022 – 2024.