2018-03-01_HYDROLOGY - C1981010 (2)

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°F` COLORADO Water Quality Assessment Department of Public '-!4 , I Health & Environment 020 Mine Water, Stormwater 40.435304 -107.519361 Middle Flume Gulch COLCLY03b Yampa River 021 Mine Water, Stormwater 40.436401 -107.515833 East Middle Flume Gulch COLCLY03b Yampa River 022 Stormwater 40.411111 -107.517777 Deal Gulch COLCLY03b Williams Fork 023 Mine Water, Stormwater 40.436111 -107.512777 East Flume Gulch COLCLY03b Yampa River 024 Stormwater 40.416944 -107.545555 West Horse Gulch COLCLY03b Williams Fork 025 Mine Water, Stormwater 40.4399 -107.500291 Deacon Gulch COLCLY03a Yampa River 026 Stormwater 40.408372 -107.512711 Deal Gulch COLCLY03b Williams Fork 027 Stormwater 40.416808 -107.498819 Jeffway Gulch COLCLY03a Williams Fork When developing permit limitations, the receiving stream and downstream segment standards should be considered in order to ensure protection of the designated uses. Where it is determined that effluent has reasonable potential to reach the downstream waterbody, the downstream segment standards must be considered. The permit limitations necessary to protect the designated uses may differ between segments based on several factors, including: difference in flow, hardness, segment standards and temporary modifications. The more restrictive limitations are adopted in the permit to protect the uses of both the immediate receiving waterbody and ensure downstream waterbodies are protected. The Trapper Mine process water outfalls discharge to dry tributaries to the Yampa River. Oak, Middle Flume, East Middle Flume, East Flume and Deacon Gulches all discharge into Deep Cut Ditch prior to reaching the Yampa River. No -Name and East Pyeatt Gulches discharge directly to the Yampa River. The dilution ratio of the Yampa River to the combined process water outfalls is 6:1. Based on the size of the permitted discharges and the distance from the outfalls to the river, it is feasible that the effluent reaches the Yampa River. Because there is potential for the facility effluent to reach the Yampa River, it is necessary to consider the Yampa River (segment COLCLY02). This segment is composed of "mainstem of the Yampa River from a point immediately below the confluence with Elkhead Creek to the confluence with the Green River." Stream segment COLCLY02 is classified for agriculture, aquatic life warm 1, recreation class E and water supply. Information used in this assessment includes data gathered from the Trapper Mine, the Division, the Colorado Division of Water Resources (DWR), the U.S. Environmental Protection Agency (EPA), the U.S. Geological Survey (USGS), and communications with the local water commissioner. The data used in the assessment consist of the best information available at the time of preparation of this WQA analysis. III. Water Quality Standards Narrative Standards Narrative Statewide Basic Standards have been developed in Section 31.11(1) of the regulations, and apply to any pollutant of concern, even where there is no numeric standard for that pollutant. Waters of the state shall be free from substances attributable to human -caused point source or nonpoint source discharges in amounts, concentrations or combinations which: for all surface waters except wetlands; (i) can settle to form bottom deposits detrimental to the beneficial uses. Depositions are stream bottom buildup of materials which include but are not limited to anaerobic sludge, mine slurry or tailings, silt, or mud; or (ii) form floating debris, scum, or other surface materials sufficient to harm existing beneficial uses; or (iii) produce color, odor, or other conditions in such a degree as to create a nuisance or harm existing beneficial uses or impart any undesirable taste to significant edible aquatic species or to the water; or (iv) are harmful to the beneficial uses or toxic to humans, animals, plants, or aquatic life; or (v) Pa e8of40 4300 Cherry Creek Drive 5., Denver, CO 80246-1530 P'303-692-2000 www.cotorado.gov/cdphe/wqcd I