Micropiles for a New Wastewater Treatment Plant

As is typical in many older Canadian cities, the City of Windsor in south-western Ontario is serviced by a combined sewer system. In this system, a mixture of wastewater and storm water is carried to the treatment plant through a single pipe.

During major storms and heavy rainfall, the pipe system was not able to carry all of the wastewater, and the excess untreated water was directly discharged into the Detroit River.

In order to improve the water quality of the river, a new retention treatment basin for wastewater was built in Windsor.

The project included the following structures:

  • an underground tank to hold and treat wastewater

  • a new collection sewer

  • a mechanical building on the river’s embankment

The site’s location posed some difficulties due to the high water table and weak soft clays that extended to a depth of approximately 30m with highly fractured bedrock underneath.

The foundation of the retention basin had to be designed for the expected pressure loads when filled and for the expected buoyancy forces caused by ground water when empty. The original design specified a deep foundation using screw piles.

However, the piles could not have been produced and supplied on time due to the tight schedule. Consequently, micropiles were chosen in order to save time and cost.

The floor slab was anchored with a total of 155 DYWIDAG Micropiles. The micropiles consisted of Ø 57mm DYWIDAG THREADBAR® with additional Ø 36 mm DYWIDAG Bar Tendons in the bond zone. In total, 5,000m of Ø 57mm DYWIDAG THREADBAR® and 800m of Ø 36 mm DYWIDAG THREADBAR® were supplied to the site.

Each DYWIDAG Micropile was designed to carry a design load of 1,920kN in compression and 1,080kN in tension. The load bearing capacity of the DYWIDAG Micropiles was continuously confirmed throughout the project by proof tests. In addition to the micropiles, DYWIDAG supplied the complete range of accessories including tensioning jacks as well as the testing equipment.

Supplytesting equipment

City of Windsor, Canada

EBS Engineering and Construction Limited, Canada

Pretium Anderson Waterloo Inc., Canada