Barrier Modification

There are five alternative types of barrier modifications.They are intended to eliminate either all or some of the negative physical, chemical and biological effects of barriers on rivers and streams by directly modifying or bypassing the structure and the impoundment. Early consultation with OMNR and the local conservation authority is recommended.

Barrier Removal

Removal involves the demolition and excavation of the man-made barrier and rehabilitation of the site to a more natural condition. It has been said by many professionals in the field of fisheries management that breaching dams and weirs is the single most important and essential step in restoring populations of species that have been degraded or on the brink of extinction. It may also be the most pragmatic alternative that protects public interest. Breaching of a barrier is intended where the structure is no longer safe, represents a significant risk of failure and environmental harm or not economically viable to maintain. Many of our aging dams are significant hazards to public safety. By removing the obstruction and restoring the area to a more natural condition, the natural physical, chemical and biological processes eventually recover. A renewed public interest in river recreation activities, such as canoeing, kayaking, fishing and rafting, sometimes evolves from barrier removal. This alternative is well suited in situations where the planning process has identified that the dam or weir no longer serves the interests of the public. Technical concerns exist in relation to managing accumulated sediment, demolition, channel rehabilitation and long-term monitoring. Usually, the decision to move forward with this alternative is based on the economic analysis of the situation. An informed position is reached through the planning process where the benefits of the barrier have been found to no longer outweigh the harm it imposes. Recent studies in the United States have shown that removal typically costs 3 to 5 times less than the cost of keeping functionally obsolete barriers. When faced with the potential financial burdens of repeated dredging, dam inspections, maintenance, repair, safety hazards and liability, the economic benefit of dam removal far outweighs the cost of keeping the barrier in place. Each barrier removal project has its own unique set of issues. Despite the benefits of dam removal, there will always be opposition within the community. Strong emotional ties, claims of historical significance and decreased property values are common issues raised during public consultation. For dams and weirs greater than 1.0m high, this alternative is typically designed and implemented by professional contractors. With large dams, extensive channel reconstruction work is required. For smaller dams and weirs, it is possible to remove the structures using volunteers and hand tools.
Costs can range from $500 for small weirs to over $200,000 for large dams. Sediment control and site restoration are important components of the removal plan that should be considered and adequately address prior to demolishing a barrier. The demolition of beaver dams is generally not a recommended alternative for rehabilitating river health. However, there are circumstances where public safety could be at risk and it is within these situations that removal is considered appropriate. Similar consideration should be given to the control of sediment during and after removal.