This report assesses the general condition of the dam with respect to safety, based on available data and on visual inspection, to determine if the dam poses hazards to human life or property. The St. Louis District has classified this dam as unsafe because of a large seep on the downstream embankment slope near the left abutment contact, and a seriously inadequate spillway that will pass only 32 percent of the Probable Maximum Flood.

Fon-du-lac Subdivision Dam was inspected by an interdisciplinary team of engineers. The purpose of the inspection was to make an assessment of the general condition of the dam with respect to safety, based upon available data and visual inspection, in order to determine if the dam poses hazards to human life or property. Failure would threaten the life and property of ten families and cause appreciable damage to two county roads. Our inspection and evaluation indicates the dam is deficient in that the spillway is inadequate. The guidelines for a dam having the above size and hazard potential require that the spillway be capable of passing a one-half PMF (Probable Maximum Flood). The Probable Maximum Flood is defined as the flood discharge that may be expected from the most severe combination of critical meteorologic and hydrologic conditions reasonably possible in the region. Considering the small volume of water impounded, the large floodplain downstream and the three groups of farm buildings downstream, one-half PMF is the appropriate spillway design flood. A 20% PMF will begin to overtop the dam. The lake and spillway are adequate to contain a 1% annual probability flood (100-year flood) without overtopping the dam.

This report was prepared under the National Program of Inspection of Non-Federal Dams. This report assesses the general condition of the dam with respect to safety, based on available data and on visual inspection, to determine if the dam poses hazards to human life or property. (Author).

This report assesses the general condition of the dam with respect to safety, based on available data and on visual inspection, to determine if the dam poses hazards to human life or property. This dam has been classified as unsafe, non-emergency by the St. Louis District as a result of the application of the following criteria: (1) Spillway will not pass 15 percent of the Probable Maximum Flood; (2) Overtopping could result in dam failure; and (3) DAm failure significantly increases the hazard to loss of life downstream.

This dam has been classified as unsafe, non-emergency by the St. Louis District as a result of the application of the following criteria: Spillways will not pass 50 percent of the Probable Maximum Flood without overtopping the dam; Overtopping of the dam could result in failure of the dam; and Dam failure significantly increases the hazard to loss of life downstream.