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Pipeline Construction

Several crews known as "spreads" will build the pipelines in sections. The plan assumes that the pipeline will be separated into five construction sections for each year of construction. The spreads will construct sections ranging in length from 120 to 160 kilometres. The shorter sections will involve construction of both the natural gas and natural gas liquids pipelines. The longer sections will involve construction of only the natural gas pipeline.

An average of 5,000 workers will be needed over the four years of construction.

Each pipeline section, or 'spread,' will have crews working on:

1. Surveying and clearing the right-of-way
2. Right-of-way preparation
3. Hauling and stringing the pipe
4. Bending the pipe
5. Welding
6. Digging the trench
7. Lowering the pipe
8. Installing valves and special fittings
9. Crossings
10. Backfilling the trench
11. Testing
12. Cleaning up

There are a number of steps in building a pipeline.

Clearing the right-of-way1. Surveying and clearing the right-of-way. The right-of-way is a narrow strip of land that contains the pipeline(s) and is where all onsite construction activities occur. It is surveyed, cleared of brush and trees, and levelled to give workers and equipment access to build, inspect and maintain the pipeline.

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Stringing the pipe2. Right-of-way preparation. The right-of-way will be graded, and ice and snow or gravel pads will be built to allow for the movement of ditchers, additional equipment, materials and other pipeline construction activities.

3. Hauling and stringing the pipe. Lengths of pipe are moved from stockpile sites to the right-of-way. They are lined up along the right-of-way, ready for welding.

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Bending the pipe4. Bending the pipe. A pipeline must cross over hills and curve around special places such as lakes and sacred sites. To accomplish this, a specialized pipe-bending machine is used to bend some pipe to the shape of the land. The pipe retains its strength and remains circular where it is bent because of the characteristics of steel and the bending techniques used.

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5. Welding. Welding is a technique where another metal is melted and used to join lengths of pipe. The area of the weld where the two pipes are joined is actually stronger than the pipe, by design.

Welding - welder and welding hutsThis step is repeated a number of times until multiple pipe sections are joined to form a pipeline. Automatic welding machines are used where possible and some hand welding also takes place. A rigorous quality assurance and quality control program is followed to ensure the strength and quality of the welding.

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Digging the trench6. Digging the trench. A trench, or ditch, must be dug to allow the pipe to bury the pipe. The way the trench is dug, and what equipment is used, depends mainly on the type of soil. Alternates include bucket wheel trenchers, like those used for the Norman Wells pipeline, and chain trenchers, like those used for the Ikhil pipeline. Other digging equipment will include backhoes.

 

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Lowering the pipe7. Lowering the pipe.
Tractors with special arms called sidebooms are used to lower the pipe into the trench. Care is taken to avoid damaging the pipe and its exterior coating.

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Installing valves and special fittings8. Installing valves and special fittings. Valves and other connections are part of a pipeline. These assemblies are installed as the pipeline is constructed. They include shut-off valves that can block off sections of the pipeline for maintenance.

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9. Crossings. A pipeline will need to cross rivers and streams, roads and other pipelines. Plans are developed in advance. Water crossings can be completed either by "open cut" techniques or by horizontal directional drilling. The selection of a crossing method depends upon site specific criteria such as fish habitat, water flow, and soil conditions such as rocks and boulders. Generally, horizontal directional drilling is selected for major river crossings where local soil conditions permit the technique.

Backfilling the trench10. Backfilling the trench.
Before testing the pipeline, the ditch is backfilled. Sometimes the excavated soil is used to fill the trench and sometimes other selected backfill is used. Care is taken to protect the pipe coating from potential damage.

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Testing - workers testing pipe integrity11. Testing. A variety of methods will be used to ensure the integrity of the assembled pipeline and to comply with code.


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Cleaning up - right-of-way after restoration12. Cleaning up. The pipeline right-of-way and temporary facilites such as camps will be reclaimed.

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