Municipal Affairs and Environment

Dam Safety Program

Background

The provincial Dam Safety Program is meant to oversee the safe management of dams in Newfoundland and Labrador. Dam safety management entails the management of risks associated with dams to public safety, infrastructure, and the environment. The principles of dam safety apply at all stages of a dam’s life cycle (design, construction, operation, and decommissioning).

There are over 600 dams in Newfoundland and Labrador. Dams in the province fall under the legislative authority of the Water Resources Act, 2002 . The primary purpose of dams in the province include: hydro power generation, drinking water supply, mine tailings management facilities, recreational use, industrial supply, flood control, and habitat enhancement.

Image of pie chart breaking down primary purpose of dams in Newfoundland, 1% for Industrial, 2% for Recreational, 4% for Other, 9% for Mining, 26% for Drinking water and %58 for Hydro

What is a Dam?

A dam is a barrier constructed for the retention of water. The province recognizes the following two definitions of a dam:

Type of DamDefinition
Canadian Dam Association (CDA) DamA barrier constructed for the retention of water, water containing any other substance, or tailings that:
  1. is capable of impounding at least 30,000 m3 of liquid;
  2. is 2.5 m or more in height when measured vertically to the top of the barrier:
    1. from the natural bed of the water body at the downstream toe of the barrier, or 
    2. from the lowest elevation at the outside limit of the barrier, where the barrier is not across a waterbody;
  3. is a dam less than 2.5 m in height or impounding less than 30,000 m3 where the consequences of dam operation or failure are likely to be unacceptable to the public or demonstrate risk to the public.
Very Small DamA barrier constructed for the retention of water, water containing any other substance, or tailings that is greater than 1.0 m and less than 2.5 m in height.
Graph of dam

The height of the dam must be measured from the top of the dam to the natural bed of the stream or watercourse at the downstream toe, or from the lowest elevation at the outside limit of the dam. The term dam is inclusive of all appurtenances and systems incidental to, necessary for, or connected with the dam. Different types of water control structures that may be classified as dams include dams, canals, weirs, tailings dam, stormwater detention or retention pond berms, dykes, and sedimentation pond berms. Please contact the Department of Municipal Affairs and Environment regarding questions on whether a structure is classified as a dam or not.




Responsibility of Dam Owners

A dam owner is the person or legal entity that is responsible for the safety of the dam. The dam owner is responsible for keeping the dam in good repair and ensuring that the structure is maintained and operated safely. Other responsibilities of a dam owner:

Type of DamResponsibility
CDA Dam
  • Provide information on the dam to this department for the provincial inventory of dams.
  • Apply for a permit under Section 48 of the Water Resources Act for construction or alterations to the dam. Permit applications can be found here.
  • Follow CDA Dam Safety Guidelines (most recent edition) best practice with respect to the design and dam safety management program for the dam. This includes determining the dam consequence classification and may include:
    • dam failure inundation mapping
    • operation, maintenance and surveillance manual
    • emergency preparedness and response plan
    • dam safety review
    • public safety risk assessment
    • inspections
    • failure mode analysis
Very Small Dam
  • Provide information on the dam to this department for the provincial inventory of dams.
  • Ensure the dam is designed according to accepted best practice using a minimum inflow design flood annual exceedance probability of 1 in 100 years.
  • Apply for a permit under Section 48 of the Water Resources Act for construction or alterations to the dam. Permit applications can be found here.
  • Demonstrate that dam operation or failure does not demonstrate a risk to the public.

Dam Owner Annual Dam Safety Report

Consequences of Dam Failure

There are many possible human or natural causes of dam failure. The human causes of dam failure include poor design and construction, improper maintenance, or inappropriate operation. Storms, earthquakes, and mudslides and other natural causes could compromise the strength of a dam and also cause a dam to fail.

The consequences of a dam failure can include:

  • Potential loss of life for the population at risk (permanent or temporary)
  • Environmental losses
  • Cultural losses
  • Infrastructure losses
  • Economic losses

According to the CDA, dams must be classified on the basis of the consequences of the dam failing. The following dam classification scheme should be used to provide guidance on the standard of care expected of dam owners and designers.

Table 1: Dam Classification

Dam Class Population at Risk
[Note 1]
Incremental Losses
Loss of Life
[Note 2]
Environmental and Cultural Values Infrastructure and Economics
Low None 0 Minimal short-term loss
No long-term loss
Low economic losses; area contains limited infrastructure or services
Significant Temporary Only Unspecified No significant loss or deterioration of fish or wildlife habitat
Loss of marginal habitat only
Restoration or compensation in kind highly possible
Losses to recreational facilities, seasonal workplaces, and infrequently used transportation routes
High Permanent 10 or Fewer Significant loss or deterioration of important fish or wildlife habitat
Restoration or compensation in kind highly possible
High economic losses affecting infrastructure, public transportation, and commercial facilities
Very high Permanent 100 or Fewer Significant loss or deterioration of critical fish or wildlife habitat
Restoration or compensation in kind possible but impractical
Very high economic losses affecting important infrastructure or services (e.g., highway, industrial facility, storage facilities for dangerous substances)
Extreme Permanent More than 100 Major loss of critical fish or wildlife habitat
Restoration or compensation in kind impossible
Extreme losses affecting critical infrastructure or services (e.g., hospital, major industrial complex, major storage facilities for dangerous substances)

Note 1. Definitions for populations at risk:

  • None – There is no identifiable population at risk, so there is no possibility of loss of life other than through unforeseeable misadventure.
  • Temporary – People are only temporarily in the dam-breach inundation zone (e.g. seasonal cottage use, passing through on transportation routes, participating in recreational activities).
  • Permanent – The population at risk is ordinarily located in the dam-breach inundation zone (e.g., as permanent residents); three consequence classes (high, very high, extreme) are proposed to allow for more detailed estimates of potential loss of life (to assist in decision-making if the appropriate is carried out)

Note 2. Implication for loss of life:

Unspecified – The appropriate level of safety required at a dam where people are temporarily at risk depends on the number of people, the exposure time, the nature of their activity, and other conditions. A higher class could be appropriate, depending on the requirements. However, the design flood requirement, for example might not be higher if the temporary population is not likely to be present during the flood season.

Source: Canadian Dam Association (CDA) “Dam Safety Guidelines, 2007” (http://www.imis100ca1.ca/cda )

Design and Approval of Dams

Dams in Newfoundland and Labrador must be designed to meet the requirements of CDA Dam Safety Guidelines using a standards-based approach. The following table provides values for the inflow design flood based on dam classification. All construction of new dams or upgrades of existing dams must be approved under Section 48 of the Water Resources Act by the Department of Municipal Affairs and Environment. Applications and fee schedules for approvals can be found here.

Table 2: Dam Design Standards

Dam Classification Annual Exceedance Probability – Design Flow
Low 1/100
Significant Between 1/100 and 1/1000
High 1/3 between 1/1000 and PMF
Very High 2/3 between 1/1000 and PMF
Extreme Probable Maximum Flood (PMF)
Source: Canadian Dam Association (CDA) “Dam Safety Guidelines, 2007” (http://www.imis100ca1.ca/cda )

Operation of Dams

The CDA Dam Safety Guidelines provides dam owners guidance on proper operation and maintenance of dams. Depending on the dam classification, there may be requirements for:

  • Dam Safety Reviews (DSR)
  • Emergency Preparedness Plans (EPP)
  • Emergency Response Plans (ERP)
  • Operation, Maintenance and Surveillance Manual (OMS Manual)
  • Annual Dam Safety Inspections

Table 3: Suggested Frequency of Dam Safety Reviews

Dam Class Frequency of Dam Safety Reviews
Low -
Significant Every 10 years
High Every 7 years
Very High Every 5 years
Extreme Every 5 years
Source: Canadian Dam Association (CDA) “Dam Safety Guidelines, 2007” (http://www.imis100ca1.ca/cda )

A Standard Operating Procedure for Water Supply Dams was developed for Newfoundland and Labrador drinking water system operators.

Dam Safety Training

The Water Resources Management Division helps to provide and facilitate dam safety training opportunities for dam owners in the province. The following links provide information to dam owners on the province’s Dam Safety Program and dam safety management best practices from past training opportunities. New training opportunities for dam owners will be announced here.

Related Links

Contact Information

Paula Dawe, P.Eng.
Manager, Dam Safety Program
pauladawe@gov.nl.ca
(709)729-4048

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