Weed Wrecks Vancouver Construction Projects

weed plant

The latest threat to major construction projects in Vancouver comes from an unusual source – a weed that busts its way through highways, medians, concrete foundations and even metal.

The Japanese knotweed plant, which was partially blamed for cost overruns for site development during the London Olympics, was added to the BC Weed Control Act last week, meaning that landowners now have a legal obligation to control it.

Jenifer Grenz, program manager for the Invasive Species Council of Metro Vancouver, says this has ramifications for the province’s building and construction industry as it can invoke a contractor’s guarantee and add substantial costs to a project.

In addition, Grenz says, an occurrence of the plant may also invoke further ramifications going forward regarding insurance.

Already, many insurance companies throughout the UK refuse to cover sites containing knotweed, and Grenz suspects some Canadian firms to follow suit in the future as insurance companies in British Columbia increasingly learn of its spread.

Knotweed is known throughout many regions in B.C. as well as in six other Canadian provinces and in 39 out of 50 states in the US. It has a preference for cool, moist areas and can often be found around riverbeds, posing a threat to bridge footings.

It was recently found growing along the banks of the Ironworkers Memorial Bridge in Metro Vancouver.

The shade-tolerant plant can also grow in areas around gravel quarries, which Grenz says poses a risk if machinery cuts the plants and then the knotwood is subsequently transported to other sites as fill material.

Indeed, efforts to eradicate the plant by cutting, shredding or mulching do more harm than good because small pieces of the plant can regenerate an entire plant.

“When you shred it, you are just turning it into a million new plants,” Grenz says.

Grenz says increasing action on the part of regional districts and municipalities to eradicate the problem is encouraging, but adds that there is a need to raise awareness among developers and contractors as well as private landowners, especially contractors who are doing pre-loads and moving material onto a construction site.

By Andrew Heaton
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