Accelerated sewer upgrade for the York region: the YDSS forcemain twinning project
At a glance
The York Region in southern Ontario, needed a resilient, sustainable sewage solution to better service the Town of Newmarket. This included upsizing the current pipeline, constructing a new forcemain to provide system redundancy, and rebuilding all associated collection and conveyancing systems. As lead designer, our solution provides additional wastewater systems and improves sewage system reliability.The challenge
The York Durham Sewage System (YDSS) Forcemain Twinning Project included preliminary site investigations through detailed design between the Newmarket Sewage Pump Station (SPS) and the Aurora SPS.
Construction planning of the 5.4kilometer (3.38 mile) tunnel needed to be minimally disruptive to the community and its rich natural environment. This included preserving the Holland River floodplain which cuts through the heart of the city. The tunnel was slated to be built under 11 river crossings, 3 railway crossings, city parks, streets and more.
Our response
Our in-house team of Environmental Assessment specialists, ecologists, geologists, hydrogeologists, structural, civil, hydraulic, electrical, and tunnel engineers all came together to establish a lean design to enhance the pipeline.
We determined construction of a purpose built, two-pass system, which would consist of a new forcemain within a microtunnel carrier pipe. The addition would transfer sewage flow to the new pipe while preserving the use of the older one.
The forcemain was constructed within the tunnel by using pre-stressed cylinder pipe segments within the precast tunnel sections for the purposes of constructing the new forcemain. While pre-stressed cylinder pipe segments are not new to forcemain construction, the placement and connection of prestressed cylinder pipe segments within the extremely long tunnel section posed a unique challenge.
In addition, we listened to the community and worked with the Region and contractor to address concerns and responded with practical solutions to traffic, noise and vibration, and aesthetic construction concerns. As a result, we were able to minimize several permanent and temporary shafts. This meant residents would have fewer road closures and detours lessening the build schedule.
The impact
By engaging a wide range of tunneling solutions including producing longer drives and approval to maintain a 20 hour per day tunnelling schedule, the work was completed in 18 months appose to the anticipated five years, and with less disruption to the public.
Thanks to collaborative thinking and complex planning capabilities the new YDSS project contains two of the longest curved microtunnels in North America. The project also delivered a state-of-the-art forcemain ready to service the community now and in the future.