Dixon Diversion Dam Hazard Potential Classification

Strategic Insights -

The proposed Dixon Diversion Dam, located on the East Fork Martin River on the Kenai Peninsula of Alaska, has undergone a hazard potential classification assessment by DOWL, a consulting company hired by the Alaska Energy Authority. The assessment was conducted in accordance with Federal Energy Regulatory Commission (FERC) guidelines, which categorize dams based on the probable loss of human life and the impacts on economic, environmental, and lifeline interests. The dam's design flood, or the maximum flood level that the dam can safely pass, was also evaluated to determine the minimum design criteria.

Key Takeaways:

  • The proposed Dixon Diversion Dam has been classified as having Low Hazard Potential, indicating that loss of human life is not anticipated, and economic impacts would be limited to the dam owner.
  • The dam's design flood was determined to be the 100-year flood, which is the lower limit for the Inflow Design Flood (IDF) recommended by FERC guidelines.
  • The steep and narrow canyon reach of the East Fork of the Martin River below the proposed diversion dam will attenuate the breach flood wave and mitigate the potential for significant adverse environmental damages.
  • A review of aerial imagery, the National Structure Inventory (NSI), and other mapping sources did not indicate any potential for loss of human life, infrastructure, or lifeline systems, or significant adverse effects on the environment.
  • The nearest structures are offset approximately 0.5 miles from the Martin River, and the area is not a high-usage zone, further reducing the potential for adverse consequences.

Statistics:

  • The proposed diversion dam will impound 34 ac-ft of water, with a maximum depth of 25 ft.
  • The flood wave from a dam failure or mis-operation would flow 3.9 miles through a steep, narrow canyon before reaching the confluence of the East Fork Martin River and the Martin River's main channel.

Sources:

  • Federal Energy Regulatory Commission guidelines (Chapter I and II of the Engineering Guidelines for the Evaluation of Hydropower Projects)
  • Alaska Energy Authority's submission to the Federal Energy Regulatory Commission (project file 62-90200-01)
  • National Structure Inventory (NSI) data
  • BLM Alaska Public Land Survey System (PLSS) Cadastral National Spatial Data Infrastructure (CadNSDI) data
  • High-resolution LiDAR imagery and terrain mapping provided by Alaska Energy Authority (attached as Attachment 1)