These guidelines are for landowners and engineers involved in dam construction, repair, alteration, removal, and transfer of property containing a dam. These activities require a Dam Safety permit from the Department of Natural Resources. The complete dam safety rules are Parts 6115.0300-0520 of the DNR Public Waters Resources rules.
What is a dam?
A dam is any artificial barrier capable of impounding water (Minnesota Administrative Rule 6115.0320). The height of a dam is the vertical distance from the natural bed of the watercourse (measured at the downstream toe of the dam) to the highest elevation at which water may be impounded during extreme flood conditions. The storage capacity of a dam is the maximum volume of water that can be impounded by the dam. Storage capacity is normally measured in acre-feet, which is the volume of water needed to cover one acre of land to a depth of one foot.
Why is a permit needed?
Dam safety permits are required to ensure the safe design, construction, operation, and maintenance of dams in order to protect the health, safety, and welfare of the public. Dams remain in place for many decades and must be designed and built properly to remain safe and functional. If improperly designed or built, a dam may fail which can cause loss of life, property damage, environmental damage, and negative economic impacts. In addition, a permit is needed to address the possible impoundment of water on another person's property, alteration of a watercourse or impacts to the environment.
Do I need a permit?
- A permit is needed from the DNR to construct, alter, repair, remove or transfer ownership of a regulated dam (Minnesota Administrative Rules 6115.0350 and 6115.0410). Regulated dams subject to existing dam safety rules are shown on the graph of dam height and impoundment storage (see figure at right or enlarged version ).
- Federally-owned dams and dams determined by the DNR to be non-hazardous are exempt from the dam safety rules.
- Dams not subject to the dam safety rules will still require state and federal permits if they involve filling of public waters or wetlands.
How do I obtain a permit application?
- To apply for a Public Waters Work Permit, please use the MNDNR Permitting and Reporting System (MPARS) or call the State Dam Safety Engineer, 651-259-5715.
- Applicants can use the information entered into the MPARS to substitute for completing parts of the joint application form, which is used by other governmental units who regulate wetlands and waters (e.g., the U.S. Army Corps of Engineers and Local Government Units who administer the Wetland Conservation Act). No information provided as part of the MPARS application needs to be filled out again as part of the joint application form - just attach your MPARS application to the joint application form. However, the other regulatory programs may require additional information that is not part of the MPARS application.
- Reviewing the application and issuing or denying the permit are normally completed in 60 days.
What is required of a permit applicant?
The applicant (dam owner or authorized agent) must:
- obtain all necessary land rights for the dam and impoundment area to the contour elevation of the top of the dam.
- understand that owning a dam brings significant responsibilities and can create liabilities in case of improper operation or dam failure.
- have the financial means to properly operate and maintain the dam.
- show that the dam will provide quantifiable benefits and will be in compliance with current environmental practice.
- obtain the services of a professional engineer registered in Minnesota, who has experience in dam engineering, to prepare the design, plans and specifications; inspect the construction; and establish operation and maintenance procedures for the structure. The permit application may be rejected if the engineer is not qualified or the design does not meet current dam safety standards. Engineering costs for a small dam typically range from 15-20% of the construction bid amount.
- obtain all other applicable permits.
What is required in a permit application?
A detailed list of items that may be needed for the design report of a new dam or enlargement can be found in Parts 6115.0410. A design report submitted with the application must include, at a minimum, the following items:
- A map with an outline of the contributing drainage area and a property ownership map showing the outline of the dam, the normal pool, and the maximum pool for the design flood event.
- A topographic survey showing proposed dam elevations that are referenced to a National Geodetic datum (NAVD 88 or NGVD 29).
- A computation of the normal and maximum impoundment volume. If a permit exemption based on a small impoundment volume is requested by the applicant, the computations must be based on a reservoir bottom contour interval of no more than two feet.
- A hydrologic/hydraulic analysis based on the hazard classification and design level approved by the DNR-EWR Dam Safety Engineer. The top of the dam must have appropriate freeboard above the design flood elevation. The spillway must be able to pass the design discharge at safe velocities to alleviate erosion on the downstream side of the dam.
- An evaluation of the consequences of a dam failure. This may require a dam break analysis determining the hazard classification and level of design standard for which the dam must be designed. The DNR-EWR Dam Safety Engineer will have to verify the hazard classification, so the designer should get this approved before proceeding with the final design and plans.
- A geotechnical analysis, including analysis of seepage, slope stability, and foundation stability. Appropriate soil borings and testing are needed to complete these analyses.
- A stress analysis of concrete, steel, or timber structural members.
- Final plans and specifications for construction that are signed and dated by the design engineer. They must include guidelines for foundation preparation, type of embankment fill, source of borrow material, and placement of fill.
The DNR Commissioner may waive certain details in permit submittals for low hazard dams sponsored by a government agency or engineered by a federal agency.
What is required after the permit is issued?
- For privately-owned dams, the permit must be recorded with the county before construction can proceed.
- The allowed construction activities will be specified in the permit.
- Before starting construction, the permittee will have to submit information on water diversions, cofferdams, erosion control measures, and construction procedures.
- The design engineer will be required to inspect the work during construction to ensure conformance with the approved design plans and specifications.
- The design engineer and permittee will be required to submit a final construction report, including as-built plans and certification of the construction.
- The dam owner will be responsible for safe operation and maintenance and may have to submit an appropriate plan for this.
- After completing construction, the owner may be required to get an "approval to impound water" from the State Dam Safety Engineer.
- An annual performance report containing instrumentation and monitoring data may be required for certain complex or hazardous dams.
- The project will have to comply with all regulations of other federal, state, or local agencies. An Environmental Assessment Worksheet (EAW) may be required by the Environmental Quality Board.
How do I transfer ownership of a dam?
Ownership transfer of a dam requires a permit from the DNR-EWR (Minnesota Administrative Rule 6115.0370). Real estate sales may involve land on which a dam is located. The purchaser of the property must be aware of the dam, the responsibilities and liabilities of owning a dam, the structural condition of the dam and the repair costs that may be involved to bring the dam up to current safety standards.
What are the permit fees?
In addition to the $300 permit application fee, an initial construction/inspection fee may be required for privately-owned dams. This fee is based on a percentage of the construction cost, as specified in the dam safety rules. For example, the fee for a $100,000 dam is $2,500, and the fee for a $1,000,000 dam is $13,500. The state may also assess a periodic inspection fee for privately-owned dams.