Award of Excellence: Orleans Watermain Link
“The City of Ottawa needed a large 900-mm diameter watermain to cross two environmentally sensitive creeks and the Rockcliffe Parkway, a key recreational area. Like several other award-winning projects this year, the project saved money and time by being innovative.” – Jury
From the October-November print edition, p. 55
The potable water supply for more than 100,000 people in the community of Orleans in Ottawa’s east end was at risk. A single large diameter feedermain, installed more than 40 years ago, serviced the area.
A similar feedermain had failed in the neighbouring community of Barrhaven in 2011, which had cut water supply to 11,000 homes and required costly emergency repairs. It led to months of water restrictions and considerable public anxiety about the safety and health of the city’s water supply system.
It was essential for the city to avoid a similar urgent situation in the Orleans community where this critical piece of infrastructure was aging and had become vulnerable. It was necessary to add a second redundant watermain feed from east to west to bring reliability to the system.
The city therefore embarked on the Orleans Watermain Link Project to install more than 7,000 metres of 914-mm diameter watermain to Orleans.
The project faced operational challenges. The most difficult and risky part was crossing Green’s Creek, an environmentally sensitive watercourse, as well as the Rockcliffe Parkway, a “scenic” gateway to Ottawa owned by the National Capital Commission.
To minimize impacts to the environment and the risk of construction delays, which could have severe impacts to the community, Stantec engineers completed substantial engineering and design analyses. They determined that horizontal directional drilling (HDD) was feasible for the 600-metre section of the watermain below Green’s Creek and the Rockcliffe Parkway.
The Orleans Watermain Link project is the first of its kind in Ottawa to use HDD for such a long crossing with such a large diameter watermain.
There were many reasons why the underground, trenchless method made sense. It was found to be the safest approach, had the least environmental impact, and could be completed in far less time than a conventional construction method.
More traditional construction methods would have triggered the need for multiple approvals by organizations such as the Ministry of the Environment, the National Capital Commission and the local conservation authority. It was estimated that obtaining NCC approval alone for a traditional, open-cut installation would have taken up to two years — too long to wait for a community in need of critical water infrastructure.
Saving a wildlife corridor
The sensitive Green’s Creek watercourse was not impacted in any way during construction. The steep, forested slopes of the creek provide an important wildlife corridor and support a wide variety of provincially and regionally rare species. Traditional construction methods would have seen the removal of vegetation, which would have had long-lasting impacts on the natural ecosystem, as well as severely impacting the stability of the adjacent roadway, which is in an area well known for unstable Leda clay.
The HDD method selected also ensured that there was no impact on downstream fish habitats. By installing the watermain pipe more than 10 metres beneath the creek bed, Stantec minimized the potential for “frac-out,” or leakage of the bentonite slurry into the creek.(Bentonite can be lethal to aquatic life.) Careful analysis and attention to detail at every stage of construction resulted in no frac-out into the creeks during construction.
The success of the project has given the City of Ottawa the confidence to consider using HDD for virtually all sizes and lengths of new watermain installation.
Project name: Orleans Watermain Link Horizontal Directional Drilling, Ottawa
Award-winning firm (prime consultant): Stantec Consulting (John Krug, P.Eng., Gregory Chochlinski, P.Eng., Gerald Bauer, P.Eng., Erez Allouche, Ph.D, P.Eng., Kevin Alemany, P.Eng., Raymond Haché, P.Eng., Sonny Sundaram, Ph.D, P.Geo., Loretta Hardwick, Maurice Best, P.Eng., Gaetan Seguin)
Owner: City of Ottawa