How Healthy Are Your Dams?
The Nova Scotia Department of Environment and Labour (DOEL) estimates there are between 400 and 600 dams in Nova Scotia. By international standards, many dams in Nova Scotia are considered small to intermediate in size. Your typical conventional dam is an earth fill embankment, or maybe a concrete or timber structure, although smaller dams sometimes have less conventional designs. All should be equipped with discharge facilities for operational flows and flood discharge.
Dams support power generation, industrial and agricultural activities, municipal water supplies and river regulation. Dams are important to the economy of Nova Scotia and healthy dams are important to the safety of the people of Nova Scotia.
Dams in Nova Scotia are regulated by DOEL through the Environment Act, but there is no specific dam legislation. Dam safety legislation currently exists in three Canadian provinces – British Columbia, Alberta, and Quebec. In the absence of specific dam legislation, the DOEL often cites compliance with the CDA Guidelines as a requirement for obtaining or renewing an operating license for a dam.
Professional engineers have been the driving force behind development of dam safety guidelines. In Canada, the industry supported Canadian Dam Association (CDA) first published the Dam Safety Guidelines in 1995 that was intended to provide a platform for consistent evaluation of dams and dam safety deficiencies with a goal of leading to design and construction improvements and to provide a basis for dam safety legislation and regulation.
So what is a healthy dam? There are arguably four essential components to a healthy dam
- A commitment by the owner to manage the dam safely.
- Commissioning of regular independent Dam Safety Reviews.
- Operations, Maintenance and Surveillance (OM&S) procedures and policies that promote safety.
- An Emergency Preparedness Plan (EPP) for dams with potentially fatal consequences during failure.
The CDA Guidelines state that responsibility for dam safety shall be clearly defined, that dams shall be classified according to the consequences of failure and that dams shall be designed to have adequately withstand both normal and extreme loads.
The independent review should occur at five and ten year intervals, depending on the classification, and is intended to provide an objective evaluation of the operational and technical health of the dam or system of dams. It addresses issues related to design and construction, potential changes in best practice, improvements in design, changes in hydrology and changes in management. The review should be performed by a qualified engineer as outlined in the CDA Guidelines.
The CDA Guidelines state a healthy dam requires OM&S procedures be prepared, implemented, followed and updated at appropriate intervals. It also outlines components of a manual necessary for dam safety.
As well, any dam whose failure could put populated areas at risk should have an EPP document that identifies emergency situations, action plans and lists resources available to respond to an emergency. The EPP should be implemented, regularly tested and updated. An EPP would normally contain flood inundation mapping developed by modeling dam failure scenarios that identify population at risk.
Requirements, policies and procedures, both technical and managerial, are outlined in the CDA Guidelines to varying levels of detail. For the most part, they have become an accepted standard in the dam safety professional community. The CDA is presently undertaking a review of the Guidelines and intends to publish a new version of dam safety “Principles” modeled on the present Guidelines and a companion Guidelines to Best Practice document. If you would like to participate, please contact your CDA provincial Director or visit the web site at www.cda.ca.
So, how healthy are your dams? Whether you are a municipality, industrial complex, sawmill, conservation authority, water commission, mine operator, institution, etc. if you design, operate or otherwise maintain a dam you should be aware of the CDA requirements. The above comments are meant only as an overview. For more detail on the CDA requirements regarding safe dam management, contact your provincial director or a consulting firm that specializes in dam safety and design.
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