Japanese knotweed – utility wrecker

With the recent news that the Government is giving up the fight on Japanese knotweed, Will Sillar’s thoughts fall to the devastation that the invasive plant can cause to the country’s utility networks.

With the ability to break through concrete, tarmac and walls with roots (rhizomes) as small as 0.6g that can grow into a full infestation, it is believed that Japanese knotweed exists in every 10 km² of land across the UK.

This being the case, we can be certain that the networks of gas, electricity and water supplies that we rely on are faced with a threat. And it is already happening.

Recently, a north London borough called on its existing contractor and knotweed specialist, Japanese Knotweed Control, after an infestation of Japanese knotweed was reported dangerously close to a street’s gas and water supplies.

Altogether, the utility supplies for three properties (comprising around a dozen individual flats) were at risk because of an infestation in the houses’ front gardens. The gas board was notified and the Local Authority quickly condemned the site, cut off the gas supply and ordered tenants to be evacuated. Japanese Knotweed Control carried out a survey, located the problem and got to work.

“The UK needs a nationally recognised standard for surveying criteria, so that any reputable expert, wherever they are, can work from a set of universally accepted, quality information.”

Over four months the knotweed contractor manually excavated the site down to around 1.5m. As only a small amount of root is capable of starting an infestation, experts have to be sure that every piece is eradicated. If it is not dealt with effectively, Japanese knotweed can grow up to 40mm a day during peak times.

They also removed walls that had been compromised by the infestation and therefore posed a health and safety risk, and stabilised the ground surrounding the utility supplies. In total, the job took 18 months from start to finish.

Without such treatment, the spread of Japanese knotweed is impossible to eliminate with household weed killers and can cause untold damage to structural work. Who is to say what would have happened if the plant was allowed to infiltrate the utility supplies further?

What, then, do utility suppliers need from the knotweed industry to avoid this happening again?

First, the UK needs a nationally recognised standard for surveying criteria, so that any reputable expert, wherever they are, can work from a set of universally accepted, quality information. If an industry standard reporting template were to be acknowledged by the utilities sector and its lenders, insurance and legal providers, then the business of knotweed remediation would be less opaque.

Secondly, there has to be one source that shows the whereabouts, extent and history of knotweed across the country. We at National Knotweed Survey (NKS) are already working on this resource that will ultimately help not just utility companies but also property owners and professionals track and then tackle the problem before a repeat of the north London borough’s situation occurs.

We are bringing together academic research, historic records, treatment records, local authority and transaction data to create the UK’s first and only comprehensive database that tracks knotweed across the country.

Despite the Government’s unwillingness to deal with the problem, we need to take concrete steps to address the issue. Given the ability to quantify it correctly it becomes easier to shape and adopt positive management and remediation strategies.

Ultimately, if the problem can be tracked and managed utility companies can continue to provide the UK’s homes without fear of this stubborn invader damaging gas, electricity and water supplies and putting lives at risk.