Download or read book National Dam Safety Program. Potosi Lake Dam (MO 30477), Mississippi - Kaskaskia - St. Louis Basin, Washington County, Missouri. Phase I Inspection Report written by Leonard M. Krazynski and published by . This book was released on 1980 with total page 54 pages. Available in PDF, EPUB and Kindle. Book excerpt: Potosi Lake Dam is an earth dam constructed for recreational purposes. The main spillway is a 3-ft dia corrugated metal pipe (CMP), or culvert, which discharges into an unlined earth channel. A 2-ft dia CMP serves as the auxiliary spillway and discharges into the same channel. A siphon (12-in. dia steel pipe) crosses the dam at about the midpoint. It crosses under the road and rests on the downstream slope. It discharges at the dam toe. The inspection and evaluation indicate that the dam is in generally poor condition. Specific deficiencies that were noted are inadequate spillway capacity, the high potential for spillway blockage, the dense growth of large trees and brush on the downstream slope and along the upstream crest, and lack of maintenance and periodic inspections. Hydrologic/Hydraulic studies indicate that the 10 percent probability-of-occurrence event (10-yr flood) will cause overtopping of the dam. These analyses also indicate that the dam will be overtopped for a hydrologic event which produces greater than eight percent of the Probable Maximum Flood.