Environmental Science & Engineering - www.esemag.com - September 2004
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Victoria takes first steps towards stormwater pollution prevention

By Winston Tang and
Becky Metivier

Above, the grit chamber is installed in the Vortechs® System. The design of the grit chamber enhances the separation process. Unobstructed access to the grit chamber, where pollutants are sequestered, makes inspection and maintenance of the system very easy.
Victoria, the capital of British Columbia, is located on the southern tip of Vancouver Island. Once a main port for trade and commerce, today the City has become a world-renowned tourist mecca, known for its moderate climate, natural beauty, and recreation sites. Environmental stewardship is a strong community value, and the protection of natural resources is essential. Preventing water quality degradation has come to the forefront of environmental concerns for the City, which has recently undertaken many stormwater pollution prevention initiatives.

Victoria’s storm drainage system discharged urban runoff directly into the adjacent harbour without any treatment. Stormwater from parking lots, roadways or industrial sites often carries sediments, oil, grease, trash and other contaminants. Left untreated, these pollutants cause great harm to the harbour and marine environment.

During a survey conducted by one federal agency, Rock Bay was identified as the most polluted bay in the Victoria and Esquimalt Harbours, and stormwater runoff was determined to be the primary source. The bay is located alongside a six-lane roadway, which serves as a major throughway into the City. The existing storm drain discharged storm flows from a 32.9- hectare (81.3 acre) area that was predominantly paved. Because of the impervious nature of the area, and the historical industrial uses of the Rock Bay region, the bay’s ecology was being contaminated.

City officials decided to take a proactive approach, and start treating the runoff at its source - the stormwater outfall at Rock Bay. Working with Consulting Engineer Troy Jones of Kerr Wood Leidal Associates, the City began a search to find a stormwater treatment system that would meet their needs. A comprehensive search for stormwater treatment systems was done in order to find one that would work within the site’s many constraints and also provide the necessary pollutant removal.

Ultimately, the Vortechs® System, a hydrodynamic separator by Vortechnics, Inc., was chosen. Non-mechanical and gravity driven, the system uses a patented combination of vortex action and flow controls to capture pollutants and retain them throughout even the most intense storm event. The Vortechs System needed to be connected to the existing infrastructure. Multiple site challenges arose. Not only would the system be installed directly underneath the roadway among the many utility and fiber-optic cables, but because of the close proximity to the shoreline, tides and high groundwater had to be considered.

The City was also limited in the amount of space available for installation. After reviewing 28 years of precipitation data, it was determined that flow from the large drainage area could reach rates of up to 880 l/s (31.1 cfs). Vortechnics offered a cast-inplace system, which was chosen for the Rock Bay site. The total system dimensions were 3.8 metres (12.5 feet) high by 5.3 metres (17.4 feet) wide by 7.4 metres (24.3 feet) long. The system was sized to treat 1100 l/s (39 cfs) while achieving an 80% annual total suspended solids (TSS) removal of particles down to the 50-micron size. The relatively small footprint of the system made it compact enough to fit into the tight site.

G&E Equipment of Sidney, British Columbia, constructed the system on site. The Vortechs System is horizontal in design. This low profile meant a shallow excavation, which decreased time during installation, and also lessened the need for dewatering in the high groundwater environment.

“Improving surface water quality has been an important goal of the City for many years,” said Gary Pleven, City of Victoria pollution abatement officer. “This passive system technology will reduce the amount of sediments, oils, and debris being released into the harbour.”

Installing the system is only the first step in ensuring stormwater pollution prevention. Like all stormwater pollutant removal systems, periodic inspection and maintenance is essential to guarantee its long-term performance. Because the Vortechs System offers unobstructed access to accumulated pollutants through a manhole on top of the system, the City will be able to easily inspect the system and perform any necessary maintenance. Main-taining the system will also be cost-effective because the shallow system has a small pump-out volume.

Preventing and controlling stormwater- borne pollution is one of the priorities of Environment Canada’s Georgia Basin Action Plan. “Mitigating non-point source pollution requires a combination of innovative approaches, from pollution prevention- based solutions in the watershed to managing water quality at the endof- pipe,” says Laura Mclean of Environment Canada.

The City of Victoria plans to stay at the forefront by continuing to install additional stormwater systems throughout the city, removing pollutants that would have previously ended up in their marine waters and ensuring a clean harbour environment that can be enjoyed by all.

Winston Tang, Ma.SC, P.E., EST is with Environmental Technologies and
Becky Metivier is with Vortechnics, Inc.
Contact e-mail: bmetivier@vortechnics.com.

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