August 26, 2010

FEATURE | Waste & Wastewater


The expansion of the water treatment plant includes construction of an ozone treatment building.

Frank J. Horgan plant in Scarborough, Ontario gets upgrade

In an almost idyllic setting at the east edge of Toronto’s Scarborough community on the shores of Lake Ontario and adjacent the scenic East Point Park, one of the largest single water treatment plant expansions in Greater Toronto is now at its midway point.

Now producing about 26 per cent of Toronto’s drinking water, the 30-year-old Frank J. Horgan Water Treatment Plant will become even more productive when the expansion is completed sometime in late 2011.

The $188-million project, which has been underway since March 2009 and includes both new construction and upgrades to the existing plant, will increase its treatment capacity by 230 megalitres per day from the present rate of 570 ML/d to 800 ML/d. The contractor is Alberici Constructors Ltd. and the consulting engineer is CM2H Hill.

Not only is the plant increasing capacity, it will be the first ever Toronto water plant where chlorine is being replaced with ozone as the primary disinfectant to control pathogens and taste and odour compounds, says Alex Vukosavljevic, water treatment manager for the city.

That’s been accomplished through the construction of a construction of an approximately 72,000-square-foot ozone treatment building and major enhancement of filters in the existing plant, he says.

“We are taking an old plant with old technology and rerouting all the water through a state-of-the-art treatment with no interruption to water production or impacting water quality.”

At the same time, a three-kilometre intake pipe into Lake Ontario will be left untouched because it was designed for future capacity when the plant was first built, says Vukosavljevic.

The need for the expansion was first identified in a joint optimization study conducted by the city and York Region, which purchases some of its water from Toronto, he says.

As with almost all water treatment projects, the expansion and upgrade of F. J. Horgan is “not a cookie cutter operation,” says Alberici project manager Aron Shea, who has an onsite project team of 25, including a CAD operator. There are 10 major subcontractors and approximately 250 tradespeople and labourers now on site, he says.

For nearby residents and drivers passing by the plant on their way to the neighbouring park, the most visible signs of the project are the large tower cranes hoisting material for the construction of the new ozone plant, which will provide “leading edge” ozone protection.

It will comprise three ozone contact tanks, five new filters — which will complement F. J. Horgan’s eight existing ones — and two backwash tanks.

During the excavation, some unstable earth and construction debris was discovered at the east side and had to be removed and stockpiled in another area of the property.

A total of 65,000 metres of backfill was used in the construction.

“Were on a critical path,” says Shea, explaining a major priority is to build up the plant on its west end so that the electrical room can be built and equipped on the third level.

Large and complex as it is, the ozone treatment building is only one component of the project, which can roughly be divided into three phases, says Shea.

It also includes the construction of a 10-megawatt standby power plant with four 50-metre-long, 100,000-litre surge tanks. “They are the largest bladder pressure vessels in Canada.”

The project’s third component, and the one that adjacent residents and drivers passing by on there way to the East Point Park are probably not aware of, is the ongoing and substantial upgrades to the existing plant.

It includes a major enhancement of its eight filters through a process that includes removing filter media and installing granular activated carbon and sand. Four treated water pumps and two raw water pumps will also be installed.

“We have to do this without interfering with the plant’s day-to-day operation,” says Shea.

Other work being carried out at F. J. Horgan includes the construction of a liquid oxygen storage pad, complete with fencing and access gates, and the installation of a new sodium bisulfate system.

For all the activity that is occurring at the plant, the contractor has maintained good relations with the adjacent residents through the efforts of a construction liaison person who keeps the local homeowner’s association aware of work that might impact their community.

“We’ve opened the lines of communication,” says construction manager Melvin McCaleb, pointing to efforts such as having delivery truck operators use alternate routes to the plant.

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