WSP worked with the City of Charlottetown to deliver the first-ever watermain lining project in the province of Prince Edward Island (PEI).

In recent years, the City of Charlottetown, PEI has experienced an increase in watermain breaks, particularly in the Parkdale area. The majority of existing watermains in this area are of Ductile Iron material, some of which date back to the mid-1950’s. Due to their mature age, these watermains are at increased risk of cracks and breaks.

The province of PEI most commonly replaces aging watermains with new PVC pipe; however, some watermains identified for renewal are in a dense area of the city, where there is significant underground congestion with utilities and other infrastructure. As such, the city decided to use Cured-In-Place-Pipe (CIPP) watermain lining due to its less invasive methodology and reduced costs.

At completion, this project rehabilitated a total of 1,000 metres of 150mm diameter watermain and 2,700 metres of 200mm diameter watermain. In addition, all valves, fittings and fire hydrants were replaced and/or upgraded, resulting in a completely renovated distribution system.

The successful completion of this project is a significant milestone for the City of Charlottetown, province of PEI and WSP, as it is the first-ever watermain lining project completed in the province. Through the collaboration of WSP’s PEI and Thornhill offices, this project demonstrated WSP’s capabilities to offer pipeline rehabilitation consulting services at a local and national scale.

150 mm diameter lining
1,000 m 1,000 m
200 mm diameter lining
2,700 m 2,700 m
Construction Cost
$2.5M $2.5M

The most common method of watermain renewal used in the City of Charlottetown and the province of PEI is open-cut watermain replacement. However, as the population grows and city centers become more densely populated, alternative forms of renewal need to be considered which can minimize impact to residents and allow municipalities to keep up with their growing volume of aging infrastructure. With this shift comes a learning curve for stakeholders such as municipalities and local residents.

The engineering challenges and lessons learned throughout this project have come as a result of adapting to this new method of renewal and its associated impacts. The city, the province, WSP and the contractor worked collaboratively to address all stakeholder concerns and project challenges in an effective and efficient manner. Two main challenges included:

Temporary Water Supply

The use of a temporary above-ground bypass system is rarely used in PEI and, if required, is only in place for short periods of time. To complete the lining of the 2.7 km of watermain, a bypass system had to be in place throughout the entire duration of construction. The city, province, and residents were unfamiliar with this technology and many detailed discussions, planning sessions, and outreach efforts were required to educate all stakeholders.

The temporary bypass is generally designed to supply potable water to residential homes through connections to exterior hose bibs. However, it was discovered that approximately 15 per cent of homes in the area were not equipped with hose bibs. To resolve this, the contractor completed the installation of exterior hose bibs prior to installing the bypass.

Following installation of the above-ground temporary bypass, disinfection of the pipes is critical, which was a significant challenge on this project. In most cases, a nearby hydrant outside of the project area is used as a supply point to feed temporary bypass. This method minimizes unnecessary or additional excavation to adjacent live mains while seamlessly allowing the connection/disconnection process. The City of Charlottetown agreed to proceed with this method on a trial basis; however, the use of a hydrant created difficulty in disinfecting the bypass system, which was unexpected. The contractor was instead able to complete a live-tap to the adjacent watermain, which resulted in successful disinfection.

This challenge and associated problem solving presented significant schedule delays; however, the contractor took the necessary measures to complete the project in a timely manner including the addition of extra crews, extending working hours and working weekends.

img-temporary above-ground bypass system

Addressing Safety Concerns

The watermains included for renewal were located in an area which is primarily residential, with select sensitive properties, such as an assisted living home and local church. These sensitive properties have much greater fire flow requirements than the nearby residential homes, and the ability to achieve this flow with the temporary bypass system was of concern to the city.

The obvious solution of increasing the diameter of the bypass pipes created increased risk of bypass breaks. Alternative strategies were put in place to effectively respond to and address any emergency situations that may arise. Firstly, valves were strategically placed along the bypass to re-direct flow in the event of an emergency. This ensured that water could be directed towards sensitive properties as required. Secondly, the contractor employed 24-hour security on the project site to ensure immediate response in the event of an emergency. Lastly, WSP and the contractor worked in close conjunction with the City of Charlottetown Fire Department to keep them apprised of the commissioning/decommissioning of bypass and of any fire hydrants that were removed from service along the mainline. In the end, no emergencies (fire or otherwise) arose; however, these strategies assured the community that adequate infrastructure was in place to respond to an unexpected event.