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Western Dam Engineering <br /> Technical Note <br /> <br /> May 2016 <br /> <br />23 <br />small dams have little to no instrumentation and only <br />periodic formal engineering inspections. Therefore, the <br />people who are at the site most often need to <br />understand the tell-tale signs of developing adverse <br />conditions. Conditions related to potential foundation <br />seepage failure mechanisms include the following <br />(example photos of some of these conditions are also <br />shown): <br /> Saturated ground or ponded water from no known <br />surface source <br /> Water-loving vegetation such as lush grass, brush, <br />willows, or cattails, particularly at a localized area. <br /> Surface staining <br /> Deposits of sediment through toe drains or adjacent <br />drainage ditches <br /> Sand boils <br /> Crack patterns in downstream dam face <br /> Bulges at or downstream of the dam toe <br /> <br />Figure 6. Underseepage at Dam Toe Rising to Surface <br />(Wyoming NRCS) <br /> <br />Figure 7. Underseepage at Dam Toe at a Colorado <br />Dam <br /> Figure 8. Presence of Phreatophytic Vegetation <br />(willow tree and cattails) in a Seepage Location 200 <br />feet below the Downstream Toe [2] <br /> Figure 9. Surface Staining from Intermittent <br />Underseepage at a Colorado Dam <br /> <br />Figure 10. Sediment Plume within a Drainage Ditch <br />along the Downstream of a Dam Toe [2]