Protecting the environment at watercourse crossings

When pipelines cross sensitive areas, such as rivers and streams, special care needs to be taken throughout the pipeline life cycle to protect the environment in those areas.

A few weeks ago, we told you about a trenchless construction method called horizontal directional drilling that can be used to minimize the environmental impact of installing pipelines across rivers. In this post, we want to take a broader look at the environmental considerations and best practices for watercourse crossings (PDF).

Environmental considerations

Greg Bryant is a senior environmental planner at TERA Environmental Consultants, a firm that works with pipeline companies to reduce the environmental impact of their projects. He provided us with a list of environmental concerns that need to be taken into account when a pipeline crosses water. Here are some of those considerations:

• The presence or absence of fish and the sensitivity of species of fish that are observed.
• Type and quality of the fish habitat that is present both at the crossing as well as in the zone of influence downstream of the crossing.
• Stability and erosion of bed and banks and approach slopes.
• Maintaining water quantity and quality both during and following construction of the pipeline.

These are just a few of the factors companies need to think about when building watercourse crossings. Other considerations may include traditional land use by Aboriginal communities. For a comprehensive list of environmental considerations, check out page 71 of this publication: Pipelines Associated Watercourse Crossings, Third Edition (PDF).

Source: The Life Cycle of Pipeline Watercourse Crossings in Canada (the link to this publication is at the bottom of this post)

Best practices for watercourse crossings 

Choosing the best place to cross

Bryant explained that choosing a location best suited to maintaining the stability and the integrity of the pipeline is the “first and foremost consideration” when planning where a pipeline will cross water.

“The crossing needs to be geotechnically sound (i.e. stable slopes and banks),” said Bryant. “The preference is to cross at a straight stretch of the river as opposed to locating the crossing on a meander bend.”

There are many other factors that need to be considered as well, including the presence of fish habitat.

Minimizing impact during construction

Generally, a crew who specializes in watercourse crossings is used during installation, Bryant explained. Here are some other construction-related best practices Bryant provided:

• Timing restrictions, when working instream, are used to avoid periods when fish and/or their eggs are present at the crossing or within the zone of disturbance downstream of the crossing.
• Trenchless crossing methods (e.g. horizontal direction drill or punch/bore) can be used if the geological conditions are suitable; the use of these techniques to install the pipeline eliminates the need to clear riparian vegetation, grade the banks and excavate a trench in the bed of the watercourse.
• Clearing of vegetation and grading of the banks and soils adjacent to the banks are minimized to reduce the potential for erosion and sediments entering the watercourse.
• Special reclamation practices are used to reduce the potential for erosion of the stream banks and to re-establish or enhance fish habitat that was present prior to construction.

Maintaining pipeline integrity during operation

Crossings and approach slopes are monitored to make sure banks and slopes remain stable, said Bryant, especially after “high streamflow events” such as floods.

There are other special steps used to keep the pipeline operating safely (in addition to regular integrity monitoring). For example, thicker pipes, special coatings and block valves can all be used. Keep checking our blog, we’ll tell you about some of those measures in a couple of weeks.

Want more info? Check out these publications:

• The Life Cycle of Pipeline Watercourse Crossings in Canada (PDF)
• Pipelines Associated Watercourse Crossings, Third Edition (PDF) 

The Canadian Energy Pipeline Association represents Canada’s transmission pipeline companies who operate approximately 115,000 kilometres of pipelines in Canada. In 2012, these energy highways moved approximately 1.2 billion barrels of liquid petroleum products and 5.1 trillion cubic feet of natural gas. Our members transport 97 per cent of Canada’s daily natural gas and onshore crude oil from producing regions to markets throughout North America.