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Interim code of practice: Temporary cofferdams and diversion channels

1.0 About this code of practice

This code of practice outlines national best practices for the installation of temporary cofferdams and diversion channels to isolate a section of a watercourse or water body in order to conduct works, undertakings and activities in the dry while maintaining the natural downstream flow and coastal currents. This document can be used in the planning, design and construction of in-water projects.

Effective worksite isolation can significantly reduce unnecessary damage to fish and fish habitat. Some potential impacts to fish and fish habitat from cofferdams and diversion channels include, but are not limited to, direct damage to substrates, the release of sediments, the loss of riparian habitat, the stranding of fish in dewatered areas and impingement/entrainment of fish at pump intakes.

In most cases, this code of practice will be referenced in requests for review of works, undertakings and activities that require site isolation. If other aspects of your project (other than the temporary cofferdam or diversion channel ) have the potential to cause impacts to fish and fish habitat that are not addressed by the measures to protect fish and fish habitat, request a project near water review.

This code does not remove nor replace the obligation to comply with all applicable statutory and regulatory requirements of the Fisheries Act, the Species at Risk Act or other federal, provincial, or municipal legislation and policy.

2.0 You can use this code of practice if:

3.0 Measures to protect fish and fish habitat

3.1 Protection of fish

3.2 Protection of fish passage

3.3 Protection of the riparian zone

3.4 Protection of aquatic habitat

3.5 Protection of fish habitat from sedimentation

3.6 Protection of fish and fish habitat from deleterious substances (including suspended sediment)

3.7 Additional measures for cofferdams

3.8 Additional measures for diversion channels

3.9 Rewatering/reflooding the isolation area (partial or complete):

4.0 Project notification

This code of practice is intended to be referenced in a request for review of works, undertakings and activities that require site isolation. When making use of this code of practice, please submit a Notification Form (PDF, 50 KB) to your regional DFO office to help us improve this fish and fish habitat protection guidance over time.

It is your Duty to Notify DFO if you have caused, or are about to cause, the unauthorized death of fish by means other than fishing and/or the harmful alteration, disruption or destruction of fish habitat. Such notifications should be directed to the Fish an Fish Habitat Protection Program.

To fill out a PDF form, you must:

  1. download it to your computer
  2. use PDF software to open it (such as, Adobe Reader or Foxit PDF)

For more information: How to download and open a PDF form

5.0 Contact us

If you have questions regarding this code of practice contact the Fish and Fish Habitat Protection Program located in your region.

6.0 Glossary

A temporary structure used to isolate and dry out an area in a watercourse or water body to allow work to be carried out in the dry while maintaining downstream flow and coastal currents.
Deleterious substance
Any substance that, if added to any water, would degrade or alter or form part of a process of degradation or alteration of the quality of that water so that it is rendered or is likely to be rendered deleterious to fish or fish habitat or to the human use of fish that frequent that water.
Diversion channels
A temporary structure used to divert water form a watercourse to conduct instream work in the dry while maintaining downstream flow.
Occurs when a fish is drawn into a water intake and cannot escape.
Occurs when a entrapped fish is held in contact with the intake screen and is unable to free itself.
Ordinary high water mark
The usual or average level to which a body of water rises at its highest point and remains for sufficient time so as to change the characteristics of the land. In flowing waters (rivers, streams) this refers to the “active channel/bank-full level” which is often the 1:2 year flood flow return level. In inland lakes, wetlands or marine environments it refers to those parts of the water body bed and banks that are frequently flooded by water so as to leave a mark on the land and where the natural vegetation changes from predominately aquatic vegetation to terrestrial vegetation (excepting water tolerant species). For reservoirs this refers to normal high operating levels (Full Supply Level).
Riparian zone
Area adjacent to streams, lakes, and wetlands that support a unique mixture of water tolerant vegetation from trees and shrubs to aquatic and herbaceous plants.
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