Laserfiche WebLink
Modeling a constant inflow using SEDCADTM is somewhat complex. The methodology <br /> suggested by SEDCADTM primary author, Pam Schwab, was used to model the impact of <br /> a constant inflow. In the current version of SEDCADTM, a fixed flow can only be input <br /> by inserting a "dummy" upstream reservoir with a watershed large enough to produce a <br /> "tank" flow, and then setting the output of the dummy reservoir as a constant "User <br /> Defined" outflow curve, independent of pool elevation in the dummy reservoir. A flow of <br /> 0.56 cfs (250 gpm) was conservatively utilized to represent the flow from the East Taylor <br /> Seep, which in reality is lower based on the seasonable availability of water. The <br /> watershed, time of concentration, and curve number utilized for this simulated flow are <br /> theoretical in natures. The synthesized 250 gpm flow was then dropped into directly into <br /> East Taylor Pond. <br /> For the reclamation case at the East Taylor Pond, the 10 year 24 hour storm produces <br /> 3.53 acre feet of runoff, and the entire storm event is contained below the principal <br /> spillway elevation. The 25 year 24 hour storm event peaks at the 6,953.49 elevation <br /> which is below the emergency spill way elevation of 6,954.0'. <br /> East Taylor Permanent Post Mine Channels <br /> The East Taylor watershed is comprised of three post-mining channels. One channel, the <br /> Taylor Ditch, conveys all the post mining surface water flows to the East Taylor Pond, <br /> while the East Taylor Ditch and Taylor Trib Ditch are tributaries to the Taylor Ditch. <br /> The locations of all three channels are presented on Map 12 and Figure Exh. 7-14ET-2. <br /> The channel profiles are presented on Map 33. <br /> Taylor Ditch <br /> The area contributory to the Taylor Ditch in some locations is less than one square mile. <br /> However, portions of this channel pass over a permanent fill, and the lower portion below <br /> the confluence with the East Taylor Ditch is larger than one square mile so the modeled <br /> storm event required by rule is the 100 year 24 hour event. The entire length of the <br /> Taylor Ditch will be riprap lined. Two stock ponds TD-I and TD-2 have been <br /> constructed inline in the channel to reduce peak flows from larger storm events, and <br /> provide a water source to support the post mine land use. <br /> A SEDCADTM model (100 Year 24 Hour Channel Demonstration model) has been <br /> included which evaluates the peak flow and total runoff volume for each of the channel <br /> segments for the 100 year, 24-hour storm event. The channel configurations for the 100 <br /> year, 24 hour storm for the Taylor Ditch summarized below. <br /> Exh. 7-ET-3 Revision Date: 3/29/21 <br /> Revision No.: TR-145 <br />