Port Alberni’s outskirts are set to get a little greener with the completion of the city’s new Bainbridge water treatment plant.
“A unique feature about the water treatment plant design is that it has a low maintenance, long lasting roof system,” said city engineer Guy Cicon of the plant scheduled to for a grand opening in December.
“It’s often called a living roof where the roof system, which is very similar to a tar and gravel roof with a membrane but there’s an additional drainage layer, a fabric and a growing medium put on top of the roof to provide a medium for growing vegetation,” explained Cicon.
When it is installed, the drough-resistant vegetation combined with the slightly sloped roof (towards the back of the building), will allow for better drainage, Cicon said.
“The roof has a slope to it and the water that lands on it will drain off slower because it will infiltrate into the growing medium and be taken up through transpiration and root systems,” he said.
The only runoff will be the excess water.
With a sticker price of $4 million (half from borrowing and half from the water reserve fund), Cicon said that the green roof will be more cost efficient in the long run, even if it’s a higher price up front.
“Ultraviolet is the biggest cause of roofs deteriorating and breaking down,” said Cicon.
“You have the longevity from the vegetative layer and the earth layer that prevents ultraviolet from degrading the typical roof system. With the green roof you take away the UV light so the membrane underneath lasts for a very long time.”
According to director of finance Cathy Rothwell, the green roof cost $165,000 per a quote from Windley Contracting. They may subcontract out the green roof.
Cicon said that’s 1.5 times the cost of a standard industrial roof but that it will increase the lifespan by much more than that.
“I’d expect a green roof to last several times longer than a typical roofing system. It will outlive a conventional roof by more than two to three times.”
The increased cost is due to the dirt and vegetation layers as well as the need for extra structural support.
It’s not just the roof that will be green; Cicon said that the city is looking into solar panels.
“They won’t power the whole building but they will provide a token amount of solar energy,” Cicon said.
That token amount of energy from the four three-by-six foot panels will provide enough to power the chlorine injector pumps.
But it’s not necessarily energy savings that he’s looking for.
“This will help the city evaluate the solar potential for other buildings in the city.”
Energy savings will be provided by the hydronic heat pump installed at Bainbridge to heat the interior of the treatment plant.
“It will take the heat from the water to heat the interior of the building,” Cicon said.
South facing windows will also help naturally heat the building, Cicon added.
“It’s called daylighting—the south facing windows will provide natral light and passive solar heat.”
The new treatment plant won’t just be green—it will be local too.
“We substituted the structural steel beams inside for locally milled fir that the Industrial Heritage Society sourced and milled for us specifically for this project at McLean Mill,” said Cicon of the 18” 30-foot beams. (shown amid the under-construction inside of the new treatment plant back in May 2015)
“It’s part of the idea of sourcing materials and labour locally for the project.”
There’s no price difference between the planned steel beams and the current fir ones, Cicon said, nor is their lifespan any shorter.
“These beams are kept out of the weather, the rain, the sun and they will last a very long time.”
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According to Rothwell, the fir beams cost $16,000 and the work was to be done by Windley Contracting.
Other than longevity and cost savings, Cicon said that a water treatment plant is especially suited to take advantage of another benefit of green roofs.
“A green roof does have a greater insulative value associated with it,” Cicon explained. “So for heat loss and heat gain it’ll keep the interior at a more constant temperature.”
That reduces the cost of running the building.
“It will cost less for heating and air conditioning the water treatment plant; you want to control the interior environment for heat and condensation.”
Controlling the temperature is important for the ultraviolet and chlorine treatment that the plant is designed to do.
“The basic water treatment process that happens here is disinfection. Our original water treatment facility had chlorine disinfection and our VIHA new regulations have required us to add a new disinfection barrier.”
“We’ve added ultraviolet disinfection to our process and we’ve switched out the chlorine gas system to a liquid chlorine system, which is much safer.”
The original chlorination plant located at the same place will continue to be used as a pump house.
The ultraviolet treatment consists of small, thin tubes that resemble light bulbs. When activated, the bacteria in the water passing through them will be destroyed by the UV rays. It was constructed by Koers Engineering at a cost of $340,154.
The regulations Cicon spoke of are the 4-3-2-1 drinking water regulations that require two treatment barriers for all surface water.
Other regulations included a turbidity of no more than one NTU. Turbidity refers to the cloudiness caused by particles in the water and can render treatment methods ineffective.
The city is currently conducting a water study to apply for a filtration waiver from VIHA. While estimates for a possible Port Alberni filtration plant are unknown, filtration plants in the Comox Valley and Nanaimo have had estimated costs from $50-70 million.