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<br /> <br /> <br /> <br />7 <br />Low Crest Areas: <br /> Causes: Settlement, early signs of piping or a void, <br />erosion, poor construction/maintenance <br /> Consequences: Reduced freeboard can lead to <br />overtopping and failure <br /> <br />Photo 14: Low crest areas (Montana DNRC) <br />Vegetation: <br /> Causes: Poor maintenance, excessive water <br />promotes growth <br /> Consequences: Obscures inspection, tree roots <br />can cause seepage paths, large trees can blow <br />over and their root systems can dislodge soil and <br />reduce freeboard <br /> <br />Photo 15: Crest vegetation (AECOM) <br />Ruts: <br /> Causes: Vehicle traffic, poor maintenance, poor <br />drainage <br /> Consequences: Seepage into embankment from <br />ponded water, loss of freeboard <br /> <br />Photo 16: Crest ruts (ASDSO) <br />Seepage <br />Since seepage can occur through the embankment, <br />foundation, abutments, or along embankment <br />penetrations, this topic will be addressed separately. <br />The most common seepage locations: <br /> Downstream slope and toe <br /> Foundation downstream of embankment <br /> Abutment groins <br /> Penetrations through embankments <br />Look for: <br /> Areas of green, lush/wetland vegetation <br /> Abrupt changes or horizontal lines of vegetation <br /> Flowing water <br /> Turbid, cloudy, or muddy water <br />Sandboils: <br /> Causes: Seepage through foundation removes <br />material, high seepage velocities cause sand to <br />“boil” <br /> Consequences: Continued seepage and erosion <br />can lead to sinkholes and foundation failure and <br />can eventually cause embankment failure <br /> <br />Photo 17: Sandboil (ASDSO) <br />Cloudy Seepage: <br /> Causes: Piping or internal erosion, internal crack, <br />pervious zone, or animal burrow; poorly <br />compacted contact between embankment and <br />abutment, seepage occurs in abutments <br /> Consequences: Progression of piping and erosion <br />of material, failure, abutment slide