National Dam Safety Program. Long Bottom Branch Dam, Inventory Number VA-02702. Buchanan County, Virginia. Phase I Inspection Report.
SCHNABEL ENGINEERING ASSOCIATES RICHMOND VA
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Long Bottom Branch Dam is a heterogeneous earthfill structure about 100 ft long and 26.5 ft high. This impoundment is a cross-valley type structure which is located on the Long Bottom Branch of Knox Creek, approximately 2.8 miles northeast of Blackey, Virginia. The roadway, which impounds water, was used as an access road for coal mining operations for the Eastern Coal Company. There is a 15 in. diameter corrugated metal pipe CMP used for the principal spillway. The dam is a small size structure and is designated a significant hazard classification. Based on criteria established by the Department of the Army, Office of the Chief of Engineers OCE, the appropriate spillway design flood SDF is the 12 Probable Maximum Flood 12 PMF. The dam will pass less than 10 of the PMF prior to being overtopped. During the SDF the dam will be overtopped by 4.2 ft for 6 hours at a critical velocity of 8.1 fps, and the spillway is considered inadequate.
- Civil Engineering