This project is situated in Keswick, Ontario which is situated on the Southeast corner of Lake Simcoe, adjacent to the popular recreational area called Cooks Bay.
The designed tunnel alignment for the Keswick Effluent Outall, resulted in the first ever combined vertical and horizontal curve microtunnel constructed in North America/Canada, and is a testament to the Engineering and Operational Skills of Ward and Burke Microtunnelling Ltd and Herrenknecht Tunnelling Equipment.
The soil conditions within the southern limits of Lake Simcoe were extremely challenging and characterized as very weak sands and silts. As a result, the project contract documents specified both microtunnelling and sealed shaft construction. The Keswick Outfall, was the first time that a microtunnel boring machine was ever used to construct a sewer outfall.
Scope of Works
- Construction of 1110m of gravity sewer using open trench excavation and microtunnelling techniques
- 800m of off-shore dredging in order to install a 48″ > 12″ ID HDPE outfall diffuser system.
- 4No. cast in situ concrete caissons were sunk from surface to formation level with tremie concrete base up to 30ft deep in locations.
The original trenchless scope of the project involved the construction of 750m of 750mm ID Sanitary sewer and six tunnelling shafts. Ward & Burke presented the General Contractor and the Client with a technical value engineered proposal of eliminating two tunnel shafts whilst ensuring that the difficult ground conditions could be dealt with successfully. The proposal included sealed caisson shaft construction and long distance microtunnelling incorporating combined curves.
Ward & Burke used the VMT SLS LT MTBM guidance system and both curved microtunnel drives were completed successfully, making the project the first trenchless project in Canada to used designed microtunnel curves along its alignment.
The project also involved the ‘wet’ retrieval of the MTBM from the bed of Lake Simcoe. The high risk tunnel drive was successfully completed, making it the first ever wet retrieval of a MBTM from a lake bed in Canada.
Awards
- Runner Up – NASTT Trenchless Project Of The Year 2013
- Ontario Public Works Association 2013 Project of The Year
- Irish Building and Design Awards – International Project of Year 2014
