Islington Avenue Trunk Watermain Rehabilitation

In 2014, the Regional Municipality of York retained WSP for the design, project management and construction administration to replace 2,000 m of 600 mm watermain and 1,000 m of 450 mm watermain, which supplies the West Woodbridge Elevated Tank. The main extends from the Region of York-City of Toronto boundary at Islington Ave and Steeles Ave W, to the intersection of Kipling Ave and Hwy No. 7. The pipeline follows an alignment up Islington Ave and across Highway 7, each four-lane regional roadways. Along the route, the watermain crosses three separate railway corridors, the Humber River, Steeles Avenue and Hwy 407 ETR.

At the outset of preliminary design, WSP completed a feasibility study to determine the optimal renewal method. Options that were considered included slip-lining, cured-in-place pipe (CIPP), and replacement by a combination of open cut and tunnel. Based on cost, minimized pedestrian and vehicular impact, ease of construction and the ability to meet desired project objectives, CIPP was selected as the preferred renewal method. In addition, the use of CIPP accommodated the various project complexities, such as the rail, river and arterial road crossings.

Cured-in-place pipe (CIPP) liner installation

Valve and chamber rehabilitation

All existing valve chambers within the limits of lining were fully rehabilitated with new components, valves, stainless steel piping and new roof slabs. Several new large valve chambers were also introduced into the pipeline to improve isolation capabilities and connections to the local distribution system.

Large Valve Chamber Rehabilitation and new valve installation

Servicing

To meet high fire-flow demands during the summer months, the Region of York required that the watermain be in service between the May long weekend and Labour Day. As such, the work was successfully phased over two winter periods: November 2017-March 2018 and November 2018-March 2019. Work through the winter months required unique consideration for the liner preparation, as the product is unable to withstand extreme cold temperatures prior to curing. In some cases, the liner “wet-out” was completed off-site in a controlled setting and transported to the project location for installation.

To increase service reliability during isolation of the watermain, the alternative supply capacity from Peel Region was expanded by twinning the existing pressure-reducing valve at a chamber located near the Region of York-Peel Region municipal boundary. This addition provided increased flow rate to the pressure district throughout construction and allowed for greater flexibility in the construction schedule into the spring of each year.

Watermain isolation

At the southern limit of the project (City of Toronto boundary), access to the existing watermain was originally intended to be achieved by excavating upstream of the City of Toronto valve chamber so as not to impact service within the City of Toronto boundaries.

Due to significant traffic and coordination challenges in this area, it was determined that access to the watermain through the chamber itself would be most logical. However, the City of Toronto required that service be maintained to all downstream areas for the duration of construction.

To resolve this issue, the City of Toronto Transmission Watermain was temporarily isolated, depressurized and drained enough to install a temporary bulkhead and structural bracing along the floor, walls and ceiling of the chamber. Once complete, the downstream Toronto valve was then re-opened and work proceeded adjacent to the live trunk watermain at the City of Toronto limit. This methodology ensured the Toronto transmission watermain remained in service and adequately chlorinated throughout construction.

Coordination

Due to the location and function of the watermain, comprehensive coordination was required with the owner (Region of York), water supplier (City of Toronto) and local distribution (City of Vaughan). It was critical to ensure that all areas would be adequately serviced throughout construction. In addition, communication and coordination with various authorities was required for work surrounding all railway, water course and highway crossings within the project limits.

Islington Avenue lining access pit adjacent to Highway 407 ETR