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<br /> <br /> <br /> <br />8 <br /> <br />Photo 18: Muddy seepage at downstream toe (ASDSO) <br />Spillways <br />Open or displaced joints on the spillway walls and slabs <br />can allow uplift pressures to develop as described <br />earlier (Photos 1 and 2). <br />Obstructions: <br /> Causes: Vegetation, floating reservoir debris <br /> Consequences: Reduced spillway capacity can <br />lead to overtopping <br /> <br />Photo 19: Vegetation obstructing spillway flow (AECOM) <br />Outlet Structures <br />Concrete Spalling, Honeycomb, Erosion: <br /> Causes: Erosion from water, poor construction, <br />freeze-thaw action <br /> Consequences: Rough concrete will erode faster; <br />exposed rebar may cause internal corrosion <br /> <br />Photo 20: Concrete erosion (AECOM) <br />Damaged Gate or Operator: <br /> Causes: Broken support block, bent/broken <br />control stem, debris stuck under gate, cracked <br />gate leaf, damaged gate seat or guides, missing <br />limit nut, improper operation (discuss with dam <br />tender) <br /> Consequences: Inability to close gate reduces <br />water storage, inability to open gate compromises <br />ability to draw down reservoir in an emergency <br /> <br />Photo 21: Bent gate stem (AECOM) <br />Erosion/Undermining: <br /> Causes: Undersized riprap or loss of riprap, no <br />energy dissipating structure at outlet <br /> Consequences: Instability of outlet structure, <br />progressive backward erosion into the <br />downstream slope