Lake Serene Dam is an earthfill structure approximately 37 ft high and 1200 ft long at the crest. The appurtenant works consist of a rock cut spillway with a concrete weir control structure located at the south abutment, and a 12-in. diameter siphon pipe located near the north end of the dam. Our inspection and evaluation indicates that the spillway does not meet the criteria set forth in the guidelines for a dam having the above size and hazard potential. The spillway will pass 27 percent of the Probable Maximum Flood without overtopping. Deficiencies visually observed by the inspection team were: (1) erosion at the contacts of the dam with the north and south abutments; (2) tree and brush growth on downstream face of dam; (3) animal burrows on face of dam; (4) concrete debris on dam face near spillway; and (5) debris in spillway outlet channel.

This dam has been classified as unsafe, non-emergency by the St. Louis District as a result of the application of the following criteria: the combined capacity of the 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.

The Von Der Ahe Dam is an earthfill structure approximately 37 ft. high and 660 ft. long at the crest. The appurtenant works consist of an 18-inch diameter concrete pipe at east abutment, a 24-inch diameter steel primary spillway pipe at Sta. 4 + 82 and a 9-inch diameter steel drawdown pipe at Sta. 4 + 95. Our inspection and evaluation indicates that the combined spillways do not meet the criteria set forth in the guidelines for a dam having the above size and hazard potential. The combined spillways will pass 33 percent of the Probable Maximum Flood without overtopping. The embankment appeared to be generally in good condition. Deficiencies visually observed by the inspection team were: (1) Erosion of downstream face at toe of embankment; (2) Erosion of upstream face of dam at elevation of primary spillway inlet; (3) Lack of trash rack on the primary spillway inlet; and (4) Apparent seepage through bedrock in the east abutment; and (5) Seepage through drain pipe valve.

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).

Lynch Lake Dam was inspected. Based on the criteria in the guidelines, the dam is in the high hazard potential classification, which means that loss of life and appreciable property loss could occur in the event of failure of the dam. The estimated damage zone extends approximately three miles downstream of the dam. Within the first two miles of the damage zone are nine dwellings, Highway NN and bridge which may be subjected to flooding, with possible damage and/or destruction, and possible loss of life. Lynch Lake Dam is in the small size classification since it is less than 40 feet high and impounds less than 1,000 acre-feet of water.

The purpose of this inspection of the Las Brisas Lake Dam 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. The guidelines used in the assessment indicate that this dam is in the high hazard potential classification. The dam is in the intermediate size classification, since it is greater than 40 ft high but less than 100 ft high. The inspection and evaluation indicate that the combined spillways do not meet the criteria set forth in the guidelines for a dam having the above size and hazard potential. The combined spillways will pass 58 percent of the Probable Maximum Flood without overtopping. The guidelines require that a dam of intermediate size with a high downstream hazard potential pass the PMF. The 100-year frequency flood will not overtop the dam. The 100-year flood is one that has a 1 percent chance of being exceeded in any given year.