Feasibility Analysis of Proposed Dam and Dam Site

DNRC recommends potential dam owners hire an engineer to conduct a feasibility analysis. This evaluation should include:

  • An assessment of soils in the reservoir pool area (can they hold water?)
  • Verify the source of water can sustain a reservoir.
  • Evaluation of the environmental and wildlife impacts if your dam will be located on a live stream. There are many factors to consider.
  • General configuration of the proposed dam (height, length, spillways, stored capacity, outlet configuration etc.)

If your dam meets the following 3 criteria, you are required to obtain permits from the Montana Dam Safety Program:

#1 Storage capacity

Dams with a storage capacity equal to or greater than 50 acre-feet, measured to normal reservoir capacity, are subject to Montana Dam Safety Act Permitting. Normal capacity is measured to the crest of the lowest ungated spillway.  For many reservoirs this is the top of the trickle tube or drop inlet.   For others, this is the crest of the auxiliary spillway.   For flood control structures, normal operating pool is always the crest of the auxiliary spillway.   For off stream reservoirs, normal operating pool is determined on a case-by-case basis.  Dams with a storage capacity of less than 50 acre-feet are not required to obtain permits.   

#2 Ownership of Property Dam is Located On

Dams that are located on non-federal property are subject to Montana Dam Safety Act Permitting. This includes state, private, irrigation districts, cities, towns and counties. Exempt are dams subject to the permitting requirements of the Federal Energy Regulatory Commission (FERC) for hydropower generation. Note there are some dams located on US Forest Service Property that lack Forest Service oversight and therefore default to Montana Dam Safety Act jurisdiction.

#3 Hazard Classification

Hazard classification refers to the potential for loss of life downstream.   A High-Hazard dam could cause loss of life, should the dam fail. High-hazard dams are required to obtain Operation and Construction permits from the Dam Safety Program.   Dams classified as “not high-hazard” are not required to obtain permits.



  • If a classification has not been done on your dam, and you meet criteria 1 & 2 above, then you should submit an Application for Determination of Hazard Classification.  An engineer from the Dam Safety Program will visit your dam site and make an assessment of the potential for loss of life downstream using survey data and dam break models. Refer to the Hazard Classification web page for more information and instructions on submitting an application.
  • Previously classified “not High-Hazard Dams” that are planning repairs or rehabilitation are required to apply for a new hazard classification, even though one has been done in the past.  Recent "red tape reduction" rule changes allow a waiver from the application process if it is obvious that no additional development has occurred downstream. Refer to the Hazard Classification web page for more information on this waiver option.

To build a new dam with an impoundment capacity of 50 acre feet or more, you must apply to the DNRC Dam Safety Program for a hazard classification and make sure your water right is in order.

It is most efficient to complete both of these activities at the same time. In order to get your water right approved, you must provide DNRC basic information about the dam (storage, height, plans for a spillway and outlet works, etc.). Sometimes, these items are changed after getting preliminary hazard classification results (it is wise, if possible, to design your reservoir to minimize what could be impacted downstream during a failure). This is one of the reasons DNRC recommends using an engineer to design the dam, pursue a water right and evaluate downstream hazards, as these all are tied together.

More information on Downstream Hazard Classification

Dams classified as high hazard, and containing over 50 acre foot of water, are required to obtain additional permits from the DNRC Dam Safety Program.

More information on Water Rights

A water right is required to legally store water.

DNRC adopted a new process based on a national model to make the construction permitting process more efficient and less prone to late-stage design changes. The process requires early involvement of the Dam Safety Program in reviewing construction designs. For more information, please refer to the Dam Construction Design Review Process.

A Construction Permit is the final stage in the Design Review Process. An application is required and must be accompanied by the engineering design report, construction plans and specifications.

Application for Construction Permit for High Hazard Dam

The dam owner is responsible for obtaining other applicable permits.  Other required permits depend on many factors including the type of dam owner (private, state, federal or local government), the owner of land under the dam (if different) and if the work is located on-stream or off-stream.  DNRC publishes an excellent reference Stream Permitting Guide that describes permits commonly needed to work on or near a body of water and who to contact for more information.
For more information please refer to Dam Safety Web Page Permitting Your Existing Dam.

Building a Small Dam (less than 50 acre-feet capacity)? 

Learn More


Rules & Laws Pertaining to Building a Dam

Montana Code Annotated

Administrative Rules of Montana

Hiring an Engineer
For a list of licensed engineers who work on dams in Montana, please contact the Dam Safety Program.