The Five Year Dam Evaluation is the Cornerstone to a Safe Dam
The Five Year Dam Evaluation is the Cornerstone to a Safe Dam

Please click on drop-down tabs below for guidance, templates and important information.

DNRC has developed Five-Year Dam Evaluation Guidelines to assist dam owners and engineers efficiently and cost effectively meet the requirements of MCA 85-15-213 and ARM 36.14.6.

Download Five Year Dam Evaluation Final Draft Guidelines

As part of the State's Red Tape Reduction efforts, the following key changes were made to the administrative rules in September 2022 that are reflected in the guidelines:

  • Clarification of terminology
  • Allow Visual Inspection to be split into two visits to the dam site, to better accommodate reservoir operation, if needed.

In addition, the guidelines reflect an effort to align the safety evaluation with downstream consequences.  Dams with lower downstream consequences have the option to conduct less rigorous analysis of hydrology, hydraulics and stability, while still meeting the intent of the administrative rules and law.

NOTE: The Guidelines are in final draft format, pending feedback from several dam owners and engineers who have volunteered to review. 

Advance preparation for the Five-Year Evaluation is critical to efficiency & cost effectiveness.

 Dam Owner Preparation Activities
  • Review Past Correspondence from Dam Safety Program
  • Pull together documentation of efforts to meet previous Operation Permit Requirements and provide to engineer.
  • Collect annual owner inspection reports and photos and provide to engineer.
  • Pull together documentation of your maintenance activities over past five years and have available to your engineer upon request.
  • Update instrumentation & monitoring records and provide access to your engineer.
  • Contact local DNRC Dam Safety Engineer to discuss schedule and DNRC expectations for the Evaluation.

To guide dam owners through preparation, DNRC has prepared a helpful questionnaire. The questionnaire summarizes key information about the dam and how the dam has been operated and maintained since the last five year evaluation. The completed questionnaire should be provided to the engineer conducting the five year dam evaluation.

Operation Permit Renewal Preparation Questionnaire - MSWord Form Fillable

Operation Permit Renewal Preparation Questionnaire -  Adobe pdf Print Version

Key preparation activities for the engineer includes:

Engineer Preparation Activities
  • Review all records provided by dam owner.
  • Review past inspection report with special attention to recommendations
  • Reach out to dam owner and DNRC for copies of past engineering analyses completed on the dam.  It may be necessary to review these as part of the Safety Evaluation.
  • Conduct a preliminary evaluation of instrumentation data following guidance in Technical Note 10.  Giving advance attention to instrumentation before conducting the Visual Inspection has multiple benefits.
  • Reserve specialized equipment if applicable (outlet inspection sled or confined space entry air meters).
  • Develop plan for outlet inspection, coordinate with dam owner (total pipe length, gate location, drop inlet location, access, precautions).

The Visual Inspection involves a complete walk over of the dam and documentation of deficiencies, maintenance needs and operational problems.  An inspection of water conveyance structures must also be done at this time, including outlet conduits and spillways (which often takes some planning).

Note: Recent Red Tape Reduction administrative rule changes provides the dam owner the flexibility to split the visual inspection into two visits to the dam, allowing outlet and spillway inspections to be completed when reservoir levels are more favorable.

The first visual inspection must be done at least 5 years from the last visual inspection, in order to be in compliance with the law.  The second visual inspection must be done before the end ot the year.  The Operation Permit Renewal is based on the second visual inspection.  This important change allows flexibility and prevents the inspection from creeping up into winter. 

An outlet conduit inspection is required Experience has repeatedly shown DNRC that inspecting the outlet conduit at least once every five years is prudent.  If your outlet is inaccessible due to the presence of a downstream gate or valve, please discuss the situation with your local DNRC Dam Safety Engineer in advance.

A review of the Operation and Maintenance Plan should include verifying that all requirements in the administrative rules are addressed:

Dam/Reservoir Operation ARM 36.14.404

(a) procedures for safe drawdown rate of the reservoir;

(b) a description of the capabilities and limitations of the outlet facilities, spillways, and other dam appurtenances;

(c) a description of the authority granted to the dam tender and the training and direction or instruction necessary to properly and safely operate the gates and other dam appurtenances during normal, flood, and emergency conditions;

(d) a description of the availability of the dam tender, means of communication between the dam tender and his supervising authority, and method of gate operation, for example, manual, automatic, or remote control;

(e) a plan to monitor and anticipate unusual weather and hydrologic conditions and incorporate these conditions into the operation plan;

(f) a plan including the method and frequency for routine inspections conducted by an engineer, or owners or dam tender, at least once per year as well as inspections after critical events identified in the plan, for example, during and after heavy runoff, a severe rainstorm, a severe wind storm, or after an earthquake, and during periods of high storage. The plan must identify an inspection checklist and other directions to complete the required inspections. Inspections following critical events must be performed by an engineer, who may also be the owner or the dam tender, experienced in dam inspection. The completed inspection checklist and any other report must be maintained in the owner's records;

(g) a plan for permanent monitoring of the dam, for example, instrument installations, seepage collection systems, and water levels necessary to ensure the safe operation of the dam. The plan must identify the frequency of the data collection and the data value(s) that would constitute an unsafe or watch condition. If no monitoring is considered necessary, the reasons for this judgment must be stated; and

(h) a plan for interaction with operations of other dams and reservoirs, upstream and downstream, that may affect or be affected by the dam or reservoir operations during normal and emergency releases.

Maintenance ARM 36.14.405

(a) the method and frequency of routine inspections and maintenance of the dam necessary to:

(i) remove and prevent the growth of trees or brush on the embankment of the dam and on the spillway system;
(ii) remove and prevent the accumulation of debris, obstructions, or other deleterious materials from upstream face of the dam and the spillway system;
(iii) ensure that all gates, orifices, dissipaters, trash racks, and other appurtenances--including monitoring devices--that affect the proper operation of the dam and reservoir are kept in good repair and working order;
(iv) maintain adequate and suitable vegetation to prevent the erosion of the embankment and earth spillway for the dam; and
(v) determine that any seepage on the downstream slopes of the dam does not present a situation indicative of potential dam failure; and

(b) a plan for a detailed record of all maintenance required, including dates and results of inspections and complete information on all maintenance, rehabilitation, and improvements. This record must also include data, including photographic documentation, on the structural behavior of the dam embankment and spillway system for all major flood and seismic events.

A review of the Emergency Action Plan should verify that all requirements in Administrative Rule 36.14.406 are addressed.

The plan must include but not be limited to:

(a) a map of the evacuation area downstream of the dam based on the estimated inundation caused by a sudden breach of the dam;

(b) an up-to-date notification directory with phone numbers of key county or municipal and emergency management officials, an engineer familiar with the dam's characteristics, the department, and a procedure to notify downstream residents located within the inundation area;

(c) the current name of the owner or representative responsible for giving notification of a threat of failure;

(d) the general sites and availability of materials for emergency repairs such as filling erosion gullies and controlling seepage; and

(e) a list of contractors and others that could provide assistance before, during, and after a dam failure or reference that the county resource book for disaster and emergency services has been examined and contains the necessary contractors and others.

The Safety Evaluation portion of the Five Year Evaluation includes the following (per ARM 36.14.602):

  • Evaluation of general condition of dam, spillways and appurtenances (from visual inspection)
  • Analysis of instrumentation
  • Review and analysis of seepage and seepage collection system
  • Review of condition of spillways and water control structures (from visual inspection)
  • Other items engineer determines necessary
  • Assessment of hydrologic and hydraulic capabilities
  • Assessment of structural stability

DNRC has been in recent discussions with the Dam Safety Community about what is an appropriate depth of analysis for the assessments of hydrology, hydraulics and stability.  Based on these consultations, DNRC has concluded that the expense of requiring the engineer to conduct detailed hydrology, hydraulics and stability analyses may not be justified for dams with a lower population at risk at every five year renewal cycle.

Moving forward, as part of Montana's Red Tape Reduction Initiative, DNRC will accept a less rigorous analyses of hydrology, hydraulics and stability for dams with lower downstream consequences.

DNRC is in the process of evaluating the population at risk located downstream of dams and will discuss their findings with dam owners and their engineer at permit renewal time.




Hydrology, Hydraulics and Stability -  High Level Analysis may be appropriate for lower consequences dams. Instead of the rigorous analysis required in the past, the following approaches can be considered:

  • A visual assessment of the downstream area and whether new development may have an impact on the spillway adequacy and other risk based dam criteria.
  • A visual assessment of existing spillways and a review of conclusions from past analyses to assess compliance with standards. In other words, is there any reason to believe that the spillways are out of compliance with state spillway standards?
  • A visual assessment of water delivery structures and review of conclusions from past analyses.  In other words, is there any reason to believe that the low level outlet and drop structures are out of compliance with current hydraulic design standards?
  • A visual assessment of the structural and geotechnical stability of the dam and foundation. In other words, are there any signs of instability that warrant a formal stability or seepage analysis?

Note:  Reasons may arise where more detail is needed.  Reasons may include evidence the dam does not meet design standards, signs of distress in the dam, or lack of a current analysis on record. DNRC will work closely with both dam owners and engineers should such a situation arise to identify a reasonable schedule for completing a needed analysis.



Hydrology, Hydraulics and Stability - Detailed Analysis  is required for higher consequences dams.  A detailed analysis typically includes:

  • A review of the breach analysis and inundation mapping.
  • A review of loss of life calculations used to determine spillway adequacy.
  • A review of the hydrologic analysis and assumptions involved to determine the Inflow Design Flood. Are the assumptions reasonable, the analysis current and free from errors?
  • A review of the hydraulic capacity and performance of both principal and auxiliary spillways and whether spillways are capable hydraulically and structurally to pass the inflow design flood with required freeboard.
  • A review of the hydraulic and structural capacity of water delivery structures, including impact basins and plunge pools. 
  • A review of the reservoir drawdown analysis and the ability of the water delivery structures to drawdown the reservoir in an emergency.
  • A review of seepage and stability analyses on record and whether the assumptions used in these analyses are reasonable and the analyses free from errors.
  • A review of the design of seepage collection and filtering systems.

Instrumentation Review

A review of instrumentation is required for all High Hazard dams regardless of consequences.  A dam's instrumentation will generally show a problem is developing long before it is observed in a Visual Inspection.

Guidance for conducting an evaluation of a dam's instrumentation is available in Technical Note 10 - Analysis of Dam Instrumentation as part of a Five Year Dam Evaluation - Working Draft. The purpose of Technical Note 10 is to summarize expectations of the Montana Dam Safety Program regarding the analysis and reporting of instrumentation data.  

Note:  Technical Note 10 is considered to be a working draft, allowing comment and feedback from the Dam Safety Community.

The Five Year Dam Evaluation Report must include the following:

1.  Documentation of the Visual Inspection (36.14.603 (1)(a))

Most engineers use a checklist to document the visual inspection, along with select photos that illustrate key points. DNRC has available a widely used checklist for documenting the Visual Inspection that can be customized for each dam.

Download Visual Inspection Checklist

Download Visual Inspection Photo Log Template

2.  Documentation of the Safety Evaluation (36.14.603 (1) (a) (c) (e))

The report must include documentation of the safety evaluations completed on the dam.  If insufficient information is available to complete the required evaluations, the report must include recommendations for additional studies, investigations and analyses. DNRC has available a new template that can be used to document the Safety Evaluation.  The template is customizable for the dam, and also includes sections to facilitate the reviews of the O&M manual and Emergency Action Plan.  Note that use of the template is optional.

As discussed above, the safety evaluation must include an Instrumentation Review where applicable.

The instrumentation review should be documented in an Instrumentation Summary Report that can be included as an appendix or an attachment.  Refer to Technical Note 10 - Analysis of Dam Instrumentation as part of a Five Year Dam Evaluation for more information. There are 4 components to an instrumentation summary report:

  1. Detailed description of all instrumentation
  2. Compilation and presentation of available instrumentation data
  3. Data analysis
  4. Summary of findings and recommendations.

Download Safety Evaluation Report Template

3.  Recommendations (36.14.603 (1) (b) (c) (e) (g))

The report must have a section that summarizes recommendations, including a suggested time period for completion. Most engineers categorize recommendations as follows:

  • High priority corrective measures or any critical or emergency measures
  • Routine actions related to maintenance or operation
  • Additional studies, investigations and analyses
  • Time period for next engineer's inspection (if less than five years, reasons must be noted)

It is important for the engineer to also note suggested updates to the O & M and EAP in their report.  An updated EAP and O&M are required for DNRC to renew the Operation Permit. If the updates are substantial and not something the dam owner can complete in a reasonable period of time potentially delaying the renewal, the EAP and O&M updates should be included as priority recommendations, with a short time frame to accomplish.

Download Safety Evaluation Report Template

4.  Safe Storage Level (36.14.603 (1) (f))

Important NoteDNRC is in discussions with the Montana engineering community about this requirement in the administrative rules.  There is broad interpretation possible, and engineers may not be able to state a "safe storage level" within the responsibilities and ethics of their profession.

Until the we resolve the interpretation of this rule, DNRC is asking engineers to state whether or not they consider it appropriate for the dam owner to continue to operate the dam at normal pool, or if a restricted level is advised for safety reasons.

Download Safety Evaluation Report Template

Optional Templates

Download Visual Inspection Checklist For items 1 above (MS Word Format)

Download Visual Inspection Photo Log Template For items 1 above (MS Word Format)

Download Safety Evaluation Report Template For items 2,3,4 above (MS Word Format)


For More information on Operation Permit Renewals please go to Permitting Your Existing Dam - Operation Permits


Rules & Laws Pertaining to Inspections/Evaluations

Montana Code Annotated (Law)

Administrative Rules and Regulations (Rules)


Download Owner Preparation Questionnaire (MS Word Format)

Download Owner Preparation Questionnaire (Adobe PDF Version)

Download Visual Inspection Checklist (MS Word Format)

Download Visual Inspection Photo Log Template (MS Word Format)

Download Safety Evaluation Report Template (MS Word Format)

Statement of Owners Intent Form (MSWord Form Fillable Document)

Statement of Owners Intent Form (Adobe pdf Print Version)