 Dams in Montana number between 3500 to 10,000. Currently 186 of the dams are designated high hazard, which is a measure of potential for downstream damage and loss of life in the event of failure. |
One common factor for all dams is the neeed for regular maintenance. No matter the size, location, or type of structure, all dams need regular inspection and upkeep to prevent failure. The intent of this page is to provide dam owners with basic maintenance information. The links provided lead to more detailed information and resources for help.
Montana's landscape is dotted with dams that range from small earthen stock ponds to the states's largest - Fort Peck Dam on the Missouri River. Over 3,500 dams are inventoried by the Department of Natural Resources Conservation (DNRC), but the more accurate number may be as high as 10,000 - 20,000. The majority of these dams are in arid eastern and central Montana, where water storage for agriculture has been necessary since the first homesteaders realized that Mother Nature didn't supply ample moisture for growing crops and raising livestock.
Dams provide for the generation of electricity, flood control, water storage for agricuture and city water supplies, and for recreation and aesthetic purposes. They are on private and public lands, and may be on-stream or off-stream.
The state of Montana classifies dams in accordance with national standards. Classification standards do not evaluate the condition of the dam, but instead consider the downstream consequences resulting from a dam failure. Three classifications are used regarding dams. Dams are classified as high hazard if there is a potential for loss of life downstream during failure. Currently, 186 dams in the state are high hazard dams. The remaining dams are classified as significant hazard dams if there is the potential for significant property or environmental damage downstream, or low hazard dams if only limimted or no property damage is likely to occur during failure.
Why is maintenance necessary?
As dams age, they become more prone to failure. Many dams in Montana were built in the '30's and '40's. Some, mostly earthen, have been around for over 100 years. As dams become more susceptible to failure, the risk to downstream reidents and property increases. The impact of failure on county resources can be great. Emergency responders, sheriffs, county road crews, commissioners and others often respond to actual dam failures, as well as to reported possible failures. The failure of this dam in Chouteau County in 2011 is an example of what can happen when corrugated metal pipe fails. Downstream damage from the released flood waters washed out a county road.
Who is responsible for dam maintenance?
Dams classified as high hazard are subject to stringent construction, maintenance and inspection requirements by the DNRC or federal agencies. The agency responsible for providing oversight is determined by the ownership status of the land where the dam is located, or if the dam is used for hydroelectric generation. However, for all dams in Montana, maintenance and repair is the responsibility of the dam owner. For more information on dam construction, maintenance, repair and permitting processes, visit the Montana DNRC Dam Safety website.
What is involved in annual inspections?
Conducting regular inspections of your dam helps to identify problems early and can save both time and money. Multiple features of both concrete and earthen embankment dams can cause problems leading to expensive repairs or a possible failure of the dam itself. The most common cause of failure in Montana involves issues with corrugated metal pipes; however, issues with concrete structures, burrowing animals, tree roots, clogged outlets, and other issues can all pose problems. Checking for damage from these sources and others should be part of every dam inspection.
A checklist for inspections can help cover all important bases. You can design your own, or use any of these sample checklists:
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Annual Inspection Checklist for Earthen Dams - fillable form
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Annual Inspection Checklist for Earthen Dams - print form
What do I do if my dam might fail?
Being proactive is the best bet. Responsible dam owner behavior includes having planned for the worst-case scenario, even for dams for small stock of fishing ponds. An Emergency Action Plan (EAP) should be in place. EAP's are required for high hazard dams. At the very least, be aware of downstream structures and infrastructures that may be impacted by released water from a failed dam. Keep a current list of names and phone numbers of downstream neighbors. Know the names and phone numbers of local emergency personnel including sheriff, county engineer and disaster emergency responders. Consider escape routes for people and animals.
What help is available to dam owners?
Montana Department of Natural Resources Conservation - Dam Safety Program - Regulates construction, operation and maintenance of dams in the state. The program also provides trainings and outreach to dam owners and engineers and works with emergency responders. Visit this website for information on inspections, permitting, obtaining names for dam engineers and more.
Pocket Safety Guide for Dams and Impoundments - This handy guide was created through joint efforts of USDA, USFS, FEMA, and NDSP
Emergency Action Plan - In the event of a dam failure, this sheet organizes pertinent contact information in one place.
Manual on Corrugated Metal Pipe in Dams - For Montana Dam Owners - This manual covers problem identification and evaluation, inspection, rehabilitation, repair and replacement.
Dam Maintenance Fact Sheets:
- Fact Sheet Packet (Contains all the titles listed below)
- Basic Dam Layout and Nomenclature
- Earthen Dam Inspection
- Dam Owner Resources
- Animal and Rodent Control
- Trees and Brush
- Dam Failure Modes
- Earthen Dam Seepage
- Earthquakes
- Upstream Slope Protection
- Groundcover
- Problems with Concrete Materials
- Concrete Repair
- Problems with Metal Materials
- Trashracks
- Inspection of Structures
- Lake Drains/Low Level Outlets
- Outlet Erosion Control
- Concrete Spillways
- Earthen Spillways