Interim standard: in-water site isolation

On this page

• About standards
• User guide
• Methods
• Glossary

1.0 About standards

Standards are 1 of a suite of tools used by the Fish and Fish Habitat Protection Program (FFHPP) to manage the risk of harmful impacts to fish and fish habitat from projects occurring in or near water. A standard specifies how to implement a specific mitigation measure (e.g., conduct all operations in isolation of open or flowing water) to achieve its objective.

Standards are not considered stand-alone documents. The conditions under which a standard can be applied, and any other applicable management measure (e.g., project must adhere to timing windows), are dictated by the regulatory or non-regulatory instrument (e.g., Codes of Practice, Regulations, Letters of Advice or Authorizations) within which it is referenced.

Standards can be referenced in an instrument, or they may also be referenced by the proponent in Requests for Review and Applications for Authorization. Provinces, territories and industry partners may also choose to reference standards in their guidelines or regulations as appropriate. If a standard cannot be implemented due to site-specific conditions or other reasons, the standard does not apply. If you are uncertain about whether you can meet a standard, it is recommended that you consult a qualified environmental professional.

Standards do 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, territorial or municipal legislation and policy including guidance regarding species and habitats managed by these jurisdictions.

2.0 User guide

This standard provides national guidance for isolating a work site when it is located in a watercourse or water body. In-water site isolation may be required to support the construction of new infrastructure or to support maintenance or removal activities associated with existing infrastructure. Some examples of projects that typically involve in-water site isolation include:

• cast-in-place concrete works associated with water intake / outfall structures, boat ramp construction and other works
• bridge and culvert installation, maintenance, replacement or removal activities
• linear infrastructure (e.g., pipeline and telecommunication lines) installation, maintenance, integrity assessment, replacement or removal activities
• shoreline or in-water dredging or excavation activities
• other in-water projects that require a temporary dry working environment

In-water site isolation is a mitigation measure that is implemented during in-water work to manage sediment laden water. The objective of the measure is to reduce the intensity, spatial scale and duration of sedimentation of fish habitat resulting from a work, undertaking and activity.

This standard provides guidance to proponents on how to implement in-water site isolation. It is intended for use in the installation, maintenance, monitoring and removal of in-water isolation methods occurring within:

• freshwater watercourses (i.e., rivers and streams)
• freshwater waterbodies (i.e., lakes and ponds)
• marine environments

The type of watercourse or water body and site-specific conditions will often inform the preferred method(s) of in-water site isolation. Some examples include:

• in-water works along water body shorelines where a dry work environment is not required can typically use a turbidity curtain to isolate the in-water work area
• in-water works within watercourses with large/coarse channel substrates may limit or prevent the effective use of steel plates to isolate the in-water work area
• in- water works within a watercourse that flows within a steep valley or bedrock may limit or prevent the effective use of a diversion channel to isolate the in-water work area

If you are uncertain about what methods should be applied based on site-specific conditions, it is recommended that you consult an expert with an appropriate professional designation.

3.0 Methods

This in-water site isolation standard includes guidance related to the following 5 methods:

1. cofferdams
2. turbidity curtains
3. pump arounds
4. flumes
5. diversion channels

3.1 Cofferdams

A cofferdam is an in-water site isolation method that is typically used along the margins of a water body or watercourse and does not impede downstream flow. A cofferdam can also be installed across a watercourse upstream and downstream of the work area. In this case, water from upstream is either pumped downstream (see Section 2.3) or directed into a temporary pipe (see Section 2.4) or temporary diversion channel (see Section 2.5). A cofferdam can be constructed using a variety of materials including rock, steel sheet pile, sandbags, concrete blocks, poly or inflatable barrier. If a dry working environment is required within the isolation area, the cofferdam materials will need to be able to create a water-tight seal. Water from within the isolation area is pumped outside of the isolation area.

3.1.1 Installation

• install the cofferdam using materials appropriate for the site conditions (e.g., rock, steel sheet pile, sandbags, concrete blocks, poly or an inflatable barrier); do not use earthen material (e.g., soil)
• select appropriate materials to create a water-tight seal around in the isolation area accounting for bank and substrate morphology and type; do not use grout
• install the cofferdam from upstream to downstream, to direct flow away from the in-water work area
• design the cofferdam to accommodate the peak seasonal flows or highest water level expected for the duration of the in-water work
• if ice is present, remove it carefully to reduce scour of the bed and banks

3.1.2 Dewatering

• safely relocate fish trapped within the site isolation work area to an appropriate location in the same watercourse or water body
  • dewater gradually to reduce the potential for stranding fish
  • capture and relocate any fish as per applicable permits
• screen intake pipes during all phases of the project
  • follow Interim code of practice: End of pipe fish protection screens for small water intakes in freshwater
• dewater the isolation area using appropriately sized pumps for the flows and seepage anticipated during construction
• pump sediment laden water into a vegetated area or a filtration system (e.g., settling basin, straw bales, filter fabric/bags)
• release filtered water gradually to reduce risk of erosion
• return water downstream, within the same watercourse or water body
• continue dewatering for the duration of in-water works or for as long as water continues to enter the isolation area

3.1.3 Maintenance and monitoring

• regularly inspect the cofferdam and dewatering system during in-water works
• repair, as needed, deficiencies observed with the cofferdam and/or dewatering system during in-water works
• regularly monitor the watercourse or water body for signs of suspended sediment during all phases of the project and take corrective action when and where required
• conduct additional relocation of fish if a breach to the isolation occurs during construction or the dewatering process

3.1.4 Removal

• remove the cofferdam following completion of in-water works
  • remove the cofferdam from downstream to upstream, to maintain water flow away from the in-water work area while allowing equalization of water levels inside and outside of the isolation area
  • remove all cofferdam materials from the watercourse or water body following completion of in-water works
• restore the bed and banks, gradient and contour affected by the project

3.2 Turbidity curtain

A turbidity curtain is an in-water site isolation method that is typically used along the margins of a water body or watercourse and does not impede downstream flow. This method is also used in the marine environment. A turbidity curtain is used in areas of low or no current that are not prone to high winds and waves. A turbidity curtain generally has a floating headline to keep the top of the curtain above the water level and a weighted bottom/anchor line/ballast chain to maintain contact with the bottom substrate. Turbidity curtains are not designed to create a dry in-water working area. Their purpose is rather to limit the dispersion of sediments in the aquatic environment during the construction period and to favour their deposition at the bottom of the water body, within an isolated area.

3.2.1 Installation

• install the turbidity curtain around the in-water work area in a manner that prevents disturbance to the bed and banks
• deploy the turbidity curtain in a manner that excludes fish from the isolation area and/or safely relocate any fish within the work area to an appropriate location in the same watercourse or water body
  • relocate any fish as per applicable permits for capturing and relocating fish
• size the turbidity curtain to manage anticipated water levels during construction

3.2.2 Maintenance and monitoring

• regularly inspect the turbidity curtain during in-water works
• repair, as needed, deficiencies observed with the turbidity curtain during in-water works
• monitor for the presence of fish within the isolation area
  • relocate any fish as per applicable permits for capturing and relocating fish
• regularly monitor the watercourse for signs of sedimentation during all phases of on-land or in-water activities and take corrective action when and where required

3.2.3 Removal

• remove the turbidity curtain from the watercourse or water body following completion of in-water works and only after suspended sediments have settled

3.3 Pump around

A pump around is an in-water site isolation method that is used when it is necessary to block the watercourse from 1 bank to the other to undertake work in the dry. Downstream flow is maintained using pumps. A cofferdam (e.g., rock, steel sheet pile, sandbags, concrete blocks, poly, inflatable barrier) is installed at the upstream and downstream ends of the work site. Water is pumped from upstream of the isolation area to a location immediately downstream of the isolation area.

3.3.1 Installation

3.3.1.1 Pumps

• install a water pumping system to transfer the natural water flow directly downstream of the in-water work site
  • install pump intakes upstream of the in-water work area with sufficient space to install the upstream cofferdam
  • install pump outlet hoses downstream of the in-water work area with sufficient space to install the downstream cofferdam
• size the pumping system to accommodate the peak seasonal flows for the duration of the in-water work
  • have back-up pumps available on-site in the event of unanticipated precipitation events or if the primary pump(s) fail
• install and operate the pump intakes and outlet hoses in a manner that prevents disturbance to the channel bed
  • follow Interim code of practice: End of pipe fish protection screens for small water intakes in freshwater
  • install energy dissipating materials (e.g., filter fabric) at the hose outlet to reduce scour and erosion of the channel substrate and bed
• operate the water pumping system continuously, whenever there is water flow, and until the in-water work is completed
• maintain downstream flow quantity and quality at all times

3.3.1.2 Cofferdam

Installation

• install cofferdam using materials appropriate for the site conditions (e.g., rock, steel sheet pile, sandbags, concrete blocks, poly or an inflatable barrier); do not use earthen material (e.g., soil)
• select appropriate materials to create a water-tight seal around in the isolation area accounting for bank and substrate morphology and type; do not use grout
• install the cofferdam from upstream to downstream, to direct flow away from the in-water work area
• design cofferdam to accommodate the peak seasonal flows or highest water level expected for the duration of the in-water work
• if ice is present, remove it carefully to reduce scour of the bed and banks

Dewatering

• safely relocate fish trapped within the site isolation work area to an appropriate location in the same watercourse or water body
  • dewater gradually to reduce the potential for stranding fish
  • capture and relocate any fish as per applicable permits
• screen intake pipes during all phases of the project
  • follow Interim code of practice: End of pipe fish protection screens for small water intakes in freshwater
• dewater the isolation area using appropriately sized pumps for the flows and seepage anticipated during construction
• pump sediment laden water into a vegetated area or a filtration system (e.g., settling basin, straw bales, filter fabric/bags)
• release filtered water gradually to reduce risk of erosion
• return water downstream, within the same watercourse or water body
• continue dewatering for the duration of in-water works or for as long as water continues to enter the isolation area

3.3.2 Maintenance and monitoring

• regularly inspect the water pumping system, cofferdam and dewatering system during in-water works
• repair, as needed, deficiencies observed with the cofferdam and/or dewatering system during in-water works
• regularly monitor the watercourse or water body for signs of suspended sediment during all phases of the project and take corrective action when and where required
• conduct additional relocation of fish if a breach to the isolation occurs during construction or the dewatering process

3.3.3 Removal

• remove the pumping system and cofferdams following completion of in-water works
  • remove the cofferdam from downstream to upstream, to maintain water flow away from the in-water work area while allowing equalization of water levels inside and outside of the isolation area
  • remove all cofferdam materials from the watercourse or water body following completion of in-water works
• restore the bed and banks, gradient and contour affected by the project

3.4 Flume

A flume (or elevated pipe) is an in-water isolation method that is used when it is necessary to block the watercourse from 1 bank to the other to undertake work in the dry. Downstream flow is maintained using a pipe, and water is conveyed downstream by force of gravity. A cofferdam (e.g., rock, steel sheet pile, sandbags, concrete blocks, poly, inflatable barrier) is installed at the upstream and downstream ends of the work site.

3.4.1 Installation

3.4.1.1 Flume

• design a flume or elevated pipe system to accommodate the peak seasonal flows for the duration of the in-water work
• install the flume in a manner that prevents disturbance to the channel bed
  • install flume intake upstream of the in-water work area with sufficient space to install the upstream cofferdam
  • install flume outlet downstream of the in-water work area with sufficient space to install the downstream cofferdam

3.4.1.2 Cofferdam

Installation

• install cofferdam using materials appropriate for the site conditions (e.g., rock, steel sheet pile, sandbags, concrete blocks, poly or an inflatable barrier); do not use earthen material (e.g., soil)
• select appropriate materials to create a water-tight seal around in the isolation area accounting for bank and substrate morphology and type; do not use grout
• install the cofferdam from upstream to downstream, to direct flow away from the in-water work area
• design cofferdam to accommodate the peak seasonal flows expected for the duration of the in-water work
• if ice is present, remove it carefully to reduce scour of the bed and banks

Dewatering

• safely relocate fish trapped within the site isolation work area to an appropriate location in the same watercourse or water body
  • dewater gradually to reduce the potential for stranding fish
  • capture and relocate any fish as per applicable permits
  • screen intake pipes during all phases of the project
  • follow Interim code of practice: End of pipe fish protection screens for small water intakes in freshwater
• dewater the isolation area using appropriately sized pumps for the flows and seepage anticipated during construction
• pump sediment laden water into a vegetated area or a filtration system (e.g., settling basin, straw bales, filter fabric/bags)
• release filtered water gradually to reduce risk of erosion
• return water downstream, within the same watercourse or water body
• continue dewatering for the duration of in-water works or for as long as water continues to enter the isolation area

3.4.2 Maintenance and monitoring

• regularly inspect the flume, cofferdam and dewatering system during in-water works
• repair, as needed, deficiencies observed with the flume, cofferdam and/or dewatering system during in-water works
• regularly monitor the watercourse or water body for signs of suspended sediment during all phases of the project and take corrective action when and where required
• conduct additional relocation of fish if a breach to the isolation occurs during construction or the dewatering process

3.4.3 Removal

• remove the flume and cofferdams following completion of in-water works
  • remove the cofferdam from downstream to upstream to maintain water flow away from the in-water work area while allowing equalization of water levels inside and outside of the isolation area
  • remove all cofferdam materials from the watercourse or water body following completion of in-water works
• restore the bed and banks, gradient and contour affected by the project

3.5 Diversion channel

A diversion channel is an in-water isolation method that uses a temporary channel constructed to convey water around the in-water isolation area and does not impede downstream flow. Use of this method is usually limited by the availability of space within which to construct a diversion channel. A cofferdam (e.g., rock, steel sheet pile, sandbags, concrete blocks, poly or an inflatable barrier) is installed at the upstream end of the work site. This method is often used in order to maintain fish passage.

3.5.1 Installation

3.5.1.1 Diversion channel

• excavate a temporary channel parallel to, and as close as possible to the existing channel, working from the downstream end to the upstream point of diversion
• line the diversion channel (e.g., poly, filter fabric, rock) if it consists of fine and/or erodible materials
• maintain hydrological conditions within the diversion channel and downstream (i.e., flow) during all phases of the project

3.5.1.2 Cofferdam

Installation

• install the cofferdam using materials appropriate for the site conditions (e.g., rock, steel sheet pile, sandbags, concrete blocks, poly or an inflatable barrier); do not use earthen material (e.g., soil)
• select appropriate materials to create a water-tight seal around in the isolation area accounting for bank and substrate morphology and type; do not use grout
• install the cofferdam from upstream to downstream, to direct flow away from the in-water work area
• design the cofferdam to accommodate the peak seasonal flows expected for the duration of the in-water work
• if ice is present, remove it carefully to reduce scour of the bed and banks

Dewatering

• safely relocate fish trapped within the site isolation work area to an appropriate location in the same watercourse or water body
  • dewater gradually to reduce the potential for stranding fish
  • capture and relocate any fish as per applicable permits
• screen intake pipes during all phases of the project
  • follow Interim code of practice: End of pipe fish protection screens for small water intakes in freshwater
• dewater the isolation area using appropriately sized pumps for the flows and seepage anticipated during construction
• pump sediment laden water into a vegetated area or a filtration system (e.g., settling basin, straw bales, filter fabric/bags)
• release filtered water gradually to reduce risk of erosion
• return water downstream, within the same watercourse or water body
• continue dewatering for the duration of in-water works or for as long as water continues to enter the isolation area

3.5.2 Maintenance and monitoring

• regularly inspect the water pumping system, cofferdam, diversion channel and dewatering (if applicable), during in-water works
• repair, as needed, deficiencies observed with the water pumping system, cofferdam, diversion channel and/or dewatering during in-water works
• regularly monitor the watercourse for signs of suspended sediment during all phases of the project and take corrective action when and where required
• conduct additional relocation of fish if a breach to the isolation occurs during construction or the dewatering process

3.5.3 Removal

• remove the cofferdams, reinstall the banks and fill in and stabilize the diversion channel to reduce erosion when no longer in use following completion of in-water works
  • remove the cofferdam from downstream to upstream to maintain water flow away from the in-water work area while allowing equalization of water levels inside and outside of the isolation area
  • remove all cofferdam materials from the watercourse or water body following completion of in-water works
• restore the bed and banks, gradient and contour affected by the project

4.0 Glossary