2020-11-12_REPORT - C1981019 - Laserfiche WebLink

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Tony Tennyson Page 3 November 12, 2020 Colowyo itself. (When considering the impacts of the Colowyo Mine on uses of the receiving waters, Colowyo's own use of the water was not considered relevant.) For the other receiving waters (Collom Gulch and Jubb Creek), there is no water supply designation in the standard. Therefore, analyses of sulfate, dissolved iron, and other parameters associated with a WS standard were not conducted for any of the creeks, and standards for these parameters are not included in Table 2. Table 2 CDPHE Water Quality Standards/Guidelines Parameter Good Spring Jubb Creek and Creek Taylor Creek Collom Gulch Standard Standard Standard Total Recoverable 1.0 mg/l 1.0 mg/1 1.0 mg/1 JR) Iron (or 1.5 m /l, see note) Dissolved Manganese 1,563 µg/l 1,563 µg/l NA Dissolved Selenium 4.6 µg/l 4.6 µg/l NA Total Recoverable 20 µg/l 20 µg/l 20 µg/l Selenium Ammonia Nitrogen 0.16 mg/1 0.16 mg/1 0.16 mg/1 Notes: For TR iron for Collom Gulch, the standard is 1.5 mg/1 during spring (March — May). For dissolved manganese, 1,563 µg/1 is chronic standard. Acute standard of 2,828 µg/1 also considered. (Both are estimates based on hardness.) For dissolved selenium, 4.6 µg/1 is chronic standard. Acute standard of 18.4 µg/1 also considered. Ammonia nitrogen is often less stringent, as it is dependent on temperature and pH (the value of 0.16 mg/1 is conservatively low). Total iron and total recoverable iron are considered synonymous within this analysis. As stated in an EPA memorandum: "Total iron data can be reported in various forms: unfiltered iron, total recoverable iron, or total iron. Based on a variety of sources, it is assumed that the term total recoverable (TREC) iron is synonymous with the term unfiltered iron. For a given sample, the concentration of TREC iron may be somewhat smaller than the concentration of total iron, but the difference is not likely large, and the EPA has, in the past, determined the two terms to be interchangeable." (Environmental Protection Agency, 1998, Memorandum from William Telliard et al., Subject: Total vs. Total Recoverable Metals.) A detailed analysis of Total Dissolved Solids (TDS) concentrations was not performed with this review. TDS concentrations in the receiving waters below the Colowyo Mine are the subject of an ongoing discussion between Tri-State and the Division, partially stemming from the Division's review of the 2017 AHR for this mine, and this potential issue will be addressed by both parties in the near future. Tri-State is also involved in a project with the Colorado Water Quality Control Division related to future treatment of the discharges into Taylor Creek.