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Microtunnelling pushes the limits

Michels has completed a project with a curved alignment, extending the limits of microtunnelling.

The MTBM head being cleaned. Image courtesy Michels.

The Michels crew completed 143 m drive under the Tualatin River in Tualatin, in the US state of Oregon, in less than a month.

The 84 inch (2,134 mm) diameter tunnel features a vertical U curve with a 198 m radius, which the company says is a record in North America for the tightest curve radius at this diameter.

Michels used a new Herrenknecht AVN 1800 machine with double-steering articulation to navigate the radius of the curve and a jacking system to install a specialised reinforced concrete pipe.

The microtunnelling drive is part of a design-build project being executed with Mortenson for water resources management utility Clean Water Services, which uses science and nature to clean water and return it to the Tualatin River, so it can be used again.

Clean Water Services is investing nearly US$70 million into its 10-year sanitary sewer program to support growth in areas of Beaverton, Tigard, Tualatin, Sherwood, unincorporated Washington County and King City, including nearby urban reserves.

The project replaced the ageing interceptor that helps control flow with more resilient and larger pipes.

This upgrade will provide a pipeline that can move 20 millions of gallons of wastewater each day and will handle capacity through 2040.

For more information visit the Michels website.

If you have a project you would like featured in Trenchless International contact Assistant Editor Chloe Jenkins at

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