A dam inspection is the examination of a dam to determine its condition and need for improved operation, maintenance, study and analyses, repairs, rehabilitation, or removal. Dam inspections are vital to identifying deficiencies at dams that may pose unacceptable dam safety risks and reducing the chance of an incident or failure. It is important that inspections be performed by those experienced and qualified in dam safety engineering. There are several types of dam inspections in accordance with the Vermont Dam Safety Rule, and the following inspections are to be performed by the Dam Safety Program or an engineer hired by the Owner:
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Periodic: A visual inspection performed at a frequency based on the hazard potential classification of the dam as noted in the Vermont Dam Safety Rule.
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Non-Periodic: A visual inspection completed outside the prescribed frequency in the Vermont Dam Safety Rule.
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Inventory: An inspection to document the configuration of the dam for input into the Vermont Dam Inventory.
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Construction: An inspection completed during construction to observe project progress and assess the work for compliance with the plans, specifications, and permit conditions.
The following inspection is to be performed by an engineer hired by the Owner:
- Comprehensive: A detailed inspection including associated studies, investigations, and analyses necessary to evaluate project risk and safety performed at a frequency based on hazard classification of the dam as noted in the Vermont Dam Safety Rule.
Periodic Inspection Program
The Dam Safety Program conducts periodic safety inspections of non-federal, non-power dams to evaluate their condition and the extent, if any, to which they pose a potential or actual threat to life, property, and the environment. An inspection report with recommendations is provided to the Owner and kept on file by the Dam Safety Program. The frequency of inspections is based on the hazard potential classification of a dam, the higher the hazard, the more often the dam inspection is required.
Hazard Potential Classification:
Hazard potential classification is based on the potential for loss of life, property losses, lifeline losses, or environmental losses if there were an incident, uncontrolled release, or failure of the dam. Hazard potential classification is independent of the condition of the dam, and it instead focuses on the potential impacts of an incident or dam failure. Hazard potential classification is dynamic and can change due to changes in downstream development (i.e. new homes or businesses built within the dam failure inundation area). The hazard potential classification could also change (either higher or lower) if a more detailed dam failure analysis is carried out that more accurately assesses downstream damage potential and losses.
The Hazard potential classification system used by the Department is similar to the U.S. Army Corps of Engineers system given in Recommended Guidelines for Safety Inspection of Dams.
| Class | Direct Loss of Life | Property losses | Lifeline losses | Environmental Losses | Inspection Frequency |
|---|---|---|---|---|---|
| High | Probable or Certain (one or more) (extensive downstream residential, commercial, or industrial development) | Not considered for this classification | Not considered for this classification | Not considered for this classification | 2 years |
| Significant | None expected | Major or extensive public and private facilities | Disruption of essential or critical facilities and access | Major or extensive mitigation required or impossible to mitigate | 5 years |
| Low | None Expected | Private agricultural lands, equipment and isolated non-occupied buildings, non-major roads | No disruption of services – repairs are cosmetic or rapidly repairable damage | Minimal incremental damage | 10 years |
| Minimal | Same as LOW hazard | None | |||
Before a periodic inspection is performed, a diligent effort is made to contact the landowner for access permission. Private property will not be accessed without permission and the landowner may deny permission for inspection.
The inspection program is currently voluntary on the part of the dam owners. Upcoming standards rules will require periodic inspections either performed by the Dam Safety Program or an engineer hired by the Owner based on above hazard potential classifications. Also, in the near future, if the Department determines that maintenance, investigation and analysis, or repairs or reconstruction of a dam are needed to comply with Department Standards and maintain the dam in a safe condition, the Owner must comply with any such requirements. See the Inspection Section for more information on dam inspections and hazard classification.
Stay tuned for more information regarding Dam Inspections!