York Durham Sewage System

Waste and┬áwetlands┬áThe heavily populated area to the east of Toronto has built a sewage system that is both fit for purpose and respectful of the residents and the natural scenery of Ontario, as John OÔÇÖHanlon discovers. The Greater Toronto Area has been growing massively since the 1960s and now has a population of 5.5 million, almost half of them born outside of Canada. And in turn, half of these immigrants have come to Canada in the last 15 years.  As well as being one of the fastest growth regions in the world, it is consequently also one of the most culturally diverse in North America, with more than 140 languages and dialects recorded. Nearly a third of Toronto residents speak a language other than English or French at home.All these people need places to live, and the lionÔÇÖs share of this expansion has been borne by the municipalities to the north and east of the city. Incremental expansion over nearly a half century may seem straightforward enough on the surface, but frequently in situations like this the provision of adequate infrastructure lags behind the pressure for industrial and residential development. Sewage and wastewater treatment in many parts of the world tend to be out of sight and out of mind, sometimes with basically 19th-century systems groaning under 21st-century demands.During the 1990s the Regional Municipality of York experienced the highest growth rate in Greater Toronto, and by 2026 the population of the Region is expected to reach 1,280,000. Back in 1965 the Province of Ontario could already see that the area would need a centralized sewage treatment system. It didnÔÇÖt want to see piecemeal development of sewage treatment plants on the Humber, Don and Rouge Rivers, so it set up the York Durham Sewage System (YDSS), which constructed a state-of-the-art wastewater collection system over the 1970s and early 1980s. The bulk of the sewage ends up at Duffin Creek Water Pollution Control Plant (WPCP), jointly owned by the York and Durham Regional authorities and located at nearby Pickering on the shores of Lake Ontario. YDSS connects municipal sewers in both York and Durham Regions to the Duffin Creek WPCP through more than 100 kilometers (62 miles) of sewer pipe. Processing thousands of gallons of wastewater daily, the plant generates vast amounts of waste, including grits and screenings waste as well as up to 20 tons of incinerator ash. The treated water is discharged into Lake Ontario.As part of the York Durham Sewage System Master Plan competed in 1997 and updated in 2002, Duffin Creek was expanded to meet the increasing flow of sewage. There have been environmental concerns in the past, including worries about the effect of all this outfall on wildfowl and the safety of local beaches. However, expansion and upgrading of the facility has contributed to YDSS now being regarded as one of the best and most environmentally friendly systems in the entire Great Lakes region.The Master Plan update identified the Lower Leslie Street Trunk and the 19th Avenue Interceptor Sewer as priority projects. The additional sewer capacity was needed to provide relief to the YDSS through Richmond Hill south of 19th Avenue. Increasing development in Aurora, Newmarket and Richmond Hill contributed to the need to classify this project as a priority project for the Region.The Regional Municipality of York finally received the necessary Certificates of Approval from the Ministry of the Environment for the York Durham Sewage Interceptor project in 2006. The project was divided into two parts: tunnelling a 4.4-kilometer, 2,100-mm one-pass reinforced concrete segmented pipe from Yonge Street along 19th Sideroad to Leslie Street and then a short distance south on that street, where it connects via transition chamber with a recently completed 1.6-kilometer sewer installed by open cut. The Leslie Street open cut section was built by Memme Construction under a separate contract.Two Lovat RME129SE tunnel-boring machines (TBMs), working in opposite directions, were used to fast-track the $76 million project while providing vital protection to environmentally sensitive Oak Ridges Moraine. They are EPB (earth pressure balance) machines, a technique that allows pressure at the face of the TBM to remain balanced. ÔÇ£Our biggest challenge has been not to do any dewatering in the area. There are also some homes on private wells,ÔÇØ says regional project manager Adrian Coombs, in describing some of the complexities faced by the main contractor, a joint venture between McNally Construction and Earth Tech, now part of AECOM, the worldÔÇÖs largest engineering consultant. Dewatering in this case meant any disturbance to the complex and unique groundwater flows in the area, varying between quicksand conditions, soft alluvial soils and even ÔÇ£glacial till upflow,ÔÇØ according to Robert Andrews, AECOMÔÇÖs president of Canadian operations. ÔÇ£This area has developed much faster than the plan foresaw, so twinning the sewer was urgent, but there had to be a major consultation exercise to satisfy environmental groups. The need to preserve surface features and the whole of the regional ecology meant we had to make use of all the newest technology available. We attracted the interest of some excellent specialist companies and created something I am sure is going to be a benchmark for future projects, not just for YDSS but all over the world.ÔÇØThe 4.3-kilometer Interceptor is only a part of York DistrictÔÇÖs grand plan. Improvements at Duffin Creek and the Southeast Collector Sewer are ongoing, and the future Upper York Sewage System will service long-term growth in East Gwillimbury, Newmarket and Aurora. Nevertheless, ÔÇ£The Interceptor sewer is one of the more critical components of the YDSS,ÔÇØ comments Bill Fisch, the CEO of York Region. ÔÇ£Our Region used leading-edge technology on this project to ensure our environment is protected and our residents and businesses experience the least disruption possible.ÔÇØ┬á ÔÇô Editorial research by Tim Conlon┬á