Great Creek Dam Failure Analysis

Project Summary

Great Creek Dam 6A is an existing earthen dam located in Brunswick County, Virginia.  The dam is approximately 65 feet high and impounds an approximate 238 acre lake. The lake is owned and maintained by the County of Brunswick and is used as a recreational facility, flood control, and water supply reservoir for Brunswick County and the Town of Lawrenceville, Virginia.  The watershed for the Great Creek Dam 6A is approximately 41.1 square miles and is comprised of mainly sparse residential development, lakes, pasture land, and forested areas. Timmons Group entered into a contract with the County of Brunswick to perform the work needed to prepare a detailed failure analysis for the dam in accordance with the Virginia Impounding Structure Regulation requirements.

Our services included the tasks to perform a detailed hydrologic analysis for the watershed draining to the dam and to a point approximately 10 miles downstream of the dam. A hydraulic analysis of the dam was performed to determine the existing outlet structure capacity and its ability to convey the required spillway design storm flow in accordance with Dam Safety regulations. A detailed dam failure analysis utilizing HEC-RAS was prepared to route the non-breach and breach storm events through the area approximately 10 miles downstream of the dam. Hazard area mapping as required by the Division of Dam Safety was prepared in order to verify the hazard classification for the dam. The dam was determined to be a High Hazard structure in accordance with Dam safety regulations.

The required Dam Safety inspection and certification forms were prepared for the dam. All information was submitted to the Division of Dam Safety in order to obtain an updated classification for the dam in accordance with the current Impounding Structure Regulation requirements.