Victoria, the provincial capital of British Columbia, is located on the southern tip of Vancouver Island. Once a main port for trade and commerce, today the City of Victoria has become a world renowned tourist destination. Environmental stewardship is a strong community value. Preventing water quality degradation has come to the forefront of environmental concerns for the city, and they have recently undertaken many stormwater pollution prevention initiatives.
As with many municipalities, the city’s storm drainage system discharged urban runoff directly into the adjacent harbor without treatment. When stormwater runs off the surfaces of parking lots, roadways or industrial sites, it carries pollutants such as sediment, oil, grease, trash and other contaminants. Left untreated, these harmful pollutants cause great harm to the harbor 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 Harbors, 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 impervious. Because of the impervious nature of the area, and the historical industrial uses of the Rock Bay region, the bay 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 the site constraints and also provide the necessary pollutant removal.
Ultimately, the Vortechs system was chosen. Non-mechanical and gravity driven, the Vortechs uses a patented combination of vortex action and flow controls to capture pollutants and retain them throughout even the most intense storm event.
Many features of the Vortechs made it the right choice for this application. Because units such as these are relatively new in Canada, it was particularly important to the consulting engineer for the system to have a documented performance record. Contech Construction Producst Inc. was the only manufacturer able to provide independent field-testing data of their system showing it was capable of meeting the necessary standards.
The installation of the system was challenging as the system had to be connected to existing infrastructure directly underneath the roadway among the many existing utilities and fiber-optic cables. Tides and high groundwater also came into consideration due to the close proximity to the shoreline.
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). Few standard size treatment systems are capable of treating flows of this magnitude, so a cast-in-place system was chosen for the Rock Bay site. The total system dimensions were 3.8-m (12.5-ft) high by 5.3-m (17.4-ft) wide by 7.4-m (24.3-ft) long. The system was sized to treat 1100 l/s (39 cfs) while achieving an 80 percent annual solids removal of particles down to the 50-micron size. The relatively small footprint of the system made it possible to fit the tight site.
G and E Equipment of Sidney, British Columbia, constructed the system on-site, and according to Mike Sedgwick, Vice President of Projects, “It was very easy to install the technology.” Unlike other available units, the Vortechs system is horizontal in design. This unique low profile meant a shallow excavation, which decreased time during installation, and also lessened the need for dewatering in the high groundwater environment.
Installing the stormwater system made Victoria one of the first cities in Canada to treat urban runoff prior to discharge into a marine 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 supplied by Contech will reduce the amount of sediments, oils, and debris being released into the harbor.”
Installation is the first step in ensuring stormwater pollution prevention. Like all stormwater pollutant removal systems, periodic inspection and maintenance of the Vortechs system 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 easily inspect the system and perform the necessary maintenance. Maintaining the system will also be cost effective because the shallow system has a small pumpout 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 end-of-pipe,” says Laura McLean of Environment Canada.
The city’s proactive approach to stormwater pollution has made them an example of environmental stewardship for the province and country. Stricter stormwater regulations for the region will follow. 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.