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).

The Upper Valle Mines Dam is an abandoned tailings dam constructed to impound sand, silt and clay tailings produced by the milling of barite ore. The dam is reported to be primarily an earth embankment with a relatively thin mantle of gravel-size tailings (chat), and cobble- to boulder-size bullrock. Both the upstream and downstream faces of the dam are heavily vegetated with brush and trees up to 18 in. diameter. The reservoir is nearly filled with fine tailings. Much of the impoundment area is densely vegetated with brush and trees. The spillway is a broad trapezoidal notch cut at the left abutment. The notch is cut into the native soil and will likely be moderately erodible during periods of flood flow. The visual inspection and evaluation of available information indicate the dam is in generally poor condition. This judgment is based on the inability of the spillway to pass the 1 percent probability-of-occurrence (100 year) flood without overtopping the embankment, the hazard of erosion posed to the embankment in the event of overtopping, the dense vegetation on the embankment, as well as the steep slopes and evidence of limited past slumping on the downstream face of the dam.

Lower Valle Mines Dam is classified as small, based on its storage capacity of 78 ac-ft. The dam is 22 ft in height. The small dam classification applies to dams between 25 and 40 ft high, or those with storage volume between 50 and 1000 ac-ft. The St. Louis District, Corps of Engineers, has classified this dam as having a high hazard potential; we concur with this classification. The estimated damage zone length extends approximately two miles downstream of the dam. Within this estimated damage zone are two improved roads, the dam and reservoir at Lake Valle, and numerous vacation and permanent dwellings on the shores of the lake. The potential for loss of life and property may be high in the event of a dam failure. Lower Valle Mines Dam is an earth dam, densely vegetated with brush and trees. There are two spillways, the main spillway on the left or west abutment and the auxiliary spillway on the east abutment. The visual inspection and evaluation of available data indicate Lower Valle Mines Dam is in generally fair condition. This judgment is based on the potential for overtopping, and the dense vegetation on the downstream face of the embankment. The embankment materials appear moderately erodible, both the vegetation presently offers some erosion protection. Seepage in the area beyond the toe of the dam does not appear to pose a hazard to the dam at this time. The lack of periodic inspections and maintenance on the dam is considered a deficiency.

This report was prepared under the National Program of Inspection of Non-Federal Dams. This report assessess 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 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.

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).