Best Management Practices for Culverts between August 1 and September 30

Follow these standard best management practices that apply to all roadwork projects.

During the reptile overwintering period from September to May, do not do any culvert work near reptile overwintering habitat that will change the water level.

When working in snake habitat, be extra cautious when replacing or working around culverts. Several species will use culverts, embankments, and the space between culverts and embankments as habitat.

When there is standing water, avoid culvert work during the active amphibian season, from March 1 to August 31.

If culvert work is necessary between May and September where turtles are nesting, either:

• Install temporary fencing before turtle nesting season to prevent turtles from nesting in the work site, or,
• Work with qualified persons to plan an alternative solution to temporary fencing, for example collecting turtle eggs, incubating them off-site, and re-introducing hatchlings after the work is completed.

Keep in-water work brief.

• Use single large culverts instead of multiple smaller ones. Larger culverts are less likely to become blocked by debris.
• Regularly monitor culverts for blockages. Follow culvert inspection procedures.
• Where beavers are causing blockages, install beaver deterrents to prevent future blockages.
• Remove debris and other obstructions that impede water flow and create barriers at culvert entrances.
• Remove debris slowly when clearing culverts to allow clean water to pass and prevent downstream sedimentation.
• Prepare a long-term maintenance plan for timely debris clearing.

On large streams (>2 metres wide) and areas with groundwater upwelling, instead of a culvert, install a bridge or arc (open-bottom) culvert.

In amphibian and reptile habitat, space culverts appropriately for the species’ migration radius: 50 metres apart for amphibians, and 150 to 300 metres apart for reptiles.

• Incorporate natural substrate or other cover elements within the structure.
• Install dry pathways within culverts, such as ~0.5 m – 1.0 m wide wildlife benches with ramps, or natural rock ledges. Place natural substrates such as branches and leaf litter on the pathways. Prioritize this in wetlands or habitats with high wildlife presence.
• Install permanent wildlife fencing to accompany culverts that also provide wildlife passage.

• Embed culverts based on the site conditions (a minimum depth of 10%) and avoid locations prone to outlet scouring.
• Ensure culvert includes a low-flow channel. Align the culvert with the streambed slope.
• Retrofit existing culverts with baffles to reduce water velocity and create resting areas within the culvert.
• Include natural substrate and other cover elements within the culvert.
• Install bridges and culverts an appropriate distance away from sensitive fish habitat: 100 metres for fish spawning areas, 500 metres from naturally reproducing brook trout lakes.

Replace any disturbed woody debris, boulders, or other natural elements fish and aquatic species might use for cover. Integrate overhanging vegetation in the bank design.

• Design culverts for water passage without causing back-flooding or perched outlets.
• In wetland areas, space culverts appropriately for the type of wetland to prevent ponding and maintain flow: 200 metres apart for bogs, 150 metres for fens, 100 metres for swamps and marshes.
• Culvert embedment must accommodate both surface and subsurface flow. In some cases, especially in wetland habitat, culverts should be embedded approximately 50%.

• Ensure the culvert is long enough to prevent fill material from obstructing the waterway.
• Ensure the culvert entrance can handle steep roadside ditch flows without overshooting the entrance.
• Plant native vegetation at culvert entrances to provide stability, shade, cover, and food sources.

At culvert entrances and exits, if soft armoring with natural vegetation will not be sufficient and long-term stabilization and rocks or rip-rap are required, ensure large gaps between rocks and rip-rap are filled with appropriate material, such as Granular B.

In deep peatlands, culverts are more likely to distort (bow) over time due to the weight of the road above. Regular monitoring and appropriate materials can help mitigate this issue​.