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<br /> <br /> <br />o Slurry wall cutoff walls are identified in the Bureau of Reclamation’s Design of Small Dams manual as <br />an effective method to protect against piping. <br /> <br />- Potential for Overtopping Failure <br />o Overtopping failure during a flood event on the South Platte River is unlikely because the embankment <br />will be nearly submerged in the backwater area of Baseline Road where shallow flooding and relatively <br />low velocities are documented in a detailed study approved by FEMA <br /> <br />Civil Resources recommends the following minor improvements to add additional protections and to improve the Site for <br />future operations: <br /> <br />- Grade / Fill: Hall-Irwin has large stockpiles of material on-site that should be used to fill-in low areas on the <br />downstream side of the subject fill areas (see picture below). This will provide protection against erosion of the <br />downstream embankment and create a larger crest width to further reduce the potential for piping or <br />overtopping failure and associated peak release rates. <br /> <br /> <br /> <br />- Overfill / Emergency Spillway: Civil Resources recommends that Hall-Irwin construct a 100-foot long grade <br />control spillway on the east side of the reservoir site, this will alleviate operational issues in the event the inflow <br />ditch or pipe malfunctions and help control flood water inflows and outflows. <br /> <br />Based on the information above and the proposed improvements, Civil Resources recommends the facility receive a No <br />Public Hazard determination by the Office of the State Engineer, Dam Safety Division. <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br />