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Western Sugar Reclamation Land Development Project <br />Flood Analysis <br />WESTERN SUGAR RECLAMATION LAND DEVELOPMENT PROJECT <br />(FILE NO. M- 2010 -049) <br />FLOOD ANALYSIS <br />October 8, 2012 <br />I. INTRODUCTION <br />As part of a September 21, 2012 meeting with the Colorado Division of Mining, Reclamation, <br />and Safety (DRMS) and Varra Companies, Inc, a PowerPoint presentation was made by Flow <br />Technologies, LLC, consultant to Varra Companies, Inc regarding the impacts of the 100 -yr <br />flood on the proposed Western Sugar Land Reclamation Project (Site). In addition, a flood <br />mitigation plan was discussed and solutions agreed upon to minimize risk of headcutting in the <br />gravel pits that may capture the Cache LaPoudre River (CLPR) should a large flood occur. <br />This report discusses flood analysis — in addition to headcutting and erosion analysis - and <br />findings by Flow Technologies, LLC as discussed in the PowerPoint presentation during the <br />September 21, 2012 meeting. A flood mitigation plan will be discussed in a separate document <br />provided by Varra Companies, Inc. <br />Note that much of the material presented is intended to satisfy the comments and concerns <br />expressed by DRMS in their letter to, Mr. Chris Varra, Varra Companies, Inc. dated February 27, <br />2012, Re: Varra Companies, Inc.; Western Sugar Reclamation Land Development Project File <br />No. M- 2010 -049; Technical Revision No. 1 (TR -01) Adequacy Review — although not discussed <br />on an item -by -item basis. <br />The methodology discussed below was performed for Tract C. However, it also applies to Tract <br />D because Tract D would receive the same flood discharge as Tract C, and also has basically the <br />same soil composition. <br />II. METHODOLOGY <br />The analysis is three -fold: (1) determine if headcutting back to river is possible using a state -of- <br />the -art dam breach erosion model, (2) determine if Tract C pit will fill via shutting pumps <br />allowing ground water inflow before erosion back to river occurs ( it is assumed that once pit is <br />full, no more erosion can occur), and (3) compare pit fill time to flood warning time. That is if <br />ample warning can be obtained allowing the pit to fill consequently stopping headcutting and <br />erosion to river, then the river will not be captured by a large flood entering the pit. <br />pg. 4 <br />