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.
A dam is a barrier constructed for the retention of water. The barrier must be at least one meter high from the top of the barrier to the natural bed of the stream or watercourse at the downstream toe of the barrier, or from the lowest elevation at the outside limit of the barrier. The term dam is inclusive of all appurtenances and systems incidental to, necessary for, or connected with the barrier. Different types of water control structures that may be classified as dams include dams, canals, weirs, tailings pond berms, stormwater pond berms, dykes, etc. Please contact the Department of Municipal Affairs and Environment regarding questions on whether a structure is classified as a dam or not.
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 following the Canadian Dam Association (CDA) Dam Safety Guidelines (most recent edition).
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:
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
|Loss of Life
|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:
Note 2. Implication for loss of life:
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|
|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)|
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:
Table 3: Suggested Frequency of Dam Safety Reviews
|Dam Class||Frequency of Dam Safety Reviews|
|Significant||Every 10 years|
|High||Every 7 years|
|Very High||Every 5 years|
|Extreme||Every 5 years|
A Standard Operating Procedure for Water Supply Dams was developed for Newfoundland and Labrador drinking water system operators.
Paula Dawe, P.Eng.
Manager, Dam Safety Program
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