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COAL <br />S� COMPANY .� <br />AEOI-LE • PR0DUCT1013'�T16¢G <br />with the hydrology of the South Taylor area It is therefore necessary to refer <br />back to the most recent previously approved TR that might have affected other <br />ditches in Table 1. For example, the data relating to West Pit Fill Ditch and East <br />Taylor Pond Ditch were last revised pursuant to TR -96, submitted July 30, 2012 <br />and approved September 27, 2012. The data in the approved Table 1 prior to the <br />changes proposed herewith via TR -97 are the data that appear in Table I in that <br />recently approved TR -96. <br />2. For the Prospect Ditch, please explain the relationships of the model <br />elements. In particular, it is unclear how subwatersheds were delineated. <br />Some are very large (subwatershed L), and some are only on one side of the <br />channel (L, M, K). Also, why does subwatershed L all drain to Structure <br />#39? Some of it should possibly drain Structure #30. <br />Colowvo's Resnonse: <br />When setting up a SEDCAD model, the first demarcation is usually the drainage <br />boundary. Next, if a particular watershed has areas of constant runoff <br />characteristics (eg. a single reclamation status condition and therefore a single <br />CN), then that will likely become a candidate for a sub - watershed. It may be one <br />of several sub - watersheds tributary to a SEDCAD "structure ", or it may be the <br />only sub - watershed tributary to that structure. The reason for this is that the <br />collection point (the SEDCAD "structure') is selected as the point at which flow <br />can arrive subject to the restriction that the flow path must generally cross the <br />contours at a perpendicular angle. In fact, that flow path is used by SEDCAD to <br />determine the time of concentration for that sub - watershed. <br />In the case of Subwatershed L, it is entirely reclaimed, all at 3+ years (CN =74). <br />Crossing the contours at right angles takes the flow down to Structure 39 as <br />overland flow, almost flowing parallel to Reach 2 of prospect Ditch, but several <br />hundred feet to the north. <br />Watersheds M and K are limited to the other side of the channel, but not because <br />they are different CN's; they are the same CN =74 for 3+ years of vegetation <br />growth as the land on Subwatershed L on the north side of Prospect Ditch. <br />However, looking at the contours it is clear that Sub - watershed K drains directly <br />into Pond PDl (perpendicular lines to the contours), while Sub - watershed M <br />must drop into the channel (Str. # 30) somewhere around Station S, again <br />constrained by the requirement to cross contours at a right angle as close as <br />practicable. <br />A Western Fuels - Colorado, LLC mining property <br />