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June 1, 2018 <br /> EARTH ENGINEERING <br /> CONSULTANTS, LLC <br /> Todd Creek Village Metro District <br /> 10450 East 159th Court <br /> Brighton. Colorado 80602 <br /> Attn: Mr. Don Summers <br /> Re: Supplemental Slope Stability Analyses <br /> Signal Reservoir—Modifications/Improvements <br /> East 168" and Quebec Street <br /> Brighton, Adams County, Colorado <br /> EEC Project No. 1122096 <br /> Mr. Summers: <br /> Enclosed, herewith, are the results of the supplemental slope stability analyses performed by <br /> Earth Engineering Consultants, LLC (EEC)personnel for the referenced project. EEC personnel <br /> previously completed a subsurface exploratiori/geotechnical engineering report for the proposed <br /> Signal Reservoir Improvement in August of 2015. For further information and findings thereof, <br /> please refer to our "Subsurface Exploration Report — Signal Reservoir Modifications <br /> Improvements" dated August 5, 2015. We have recently been requested to conduct a <br /> supplemental slope stability analyses which consisted of analyzing for a 3:1 slope at the toe of <br /> the existing and/or modified dam embankment to a depth of about 30 feet below existing site <br /> grades. We have appended a copy of the cross-sectional dam layout as well as the output <br /> diagrams from the most recent slope stability analyses. <br /> Based on our stability analyses, the critical slip surfaces were found at high water level (Steady <br /> State Figure), end of construction (EOC Figure), rapid drawdown (RDD Figure), and seismic <br /> (Seismic Figure). The safety factors at the critical slip locations are summarized in the table <br /> below along with the approach method and soil conditions (drained or undrained). The <br /> minimum safety factors were found to be greater than required by the State of Colorado <br /> Department of Water Resources, Table 5.5. <br /> 4396 GREENFIELD DRIVE <br /> WINDSOR, COLORADO 80550 <br /> (970) 545-3908 FAX (970) 663-0282 <br /> www earth-engineering corn <br />