Your browser is no longer supported

For the best possible experience using our website we recommend you upgrade to a newer version or another browser.

Your browser appears to have cookies disabled. For the best experience of this website, please enable cookies in your browser

We'll assume we have your consent to use cookies, for example so you won't need to log in each time you visit our site.
Learn more

Risk assessments: don't accept them at face value

A landmark court case has illustrated the environmental and legal risks for contractors who accept risk assessments from site operators without making their own investigations.

The case saw the first ever prosecution for gas emissions from landfill, when a large number of perimeter boreholes on the Hermitage Landfill site near Newbury exceeded the permitted levels for methane and CO2

Waste Recycling Group (WRG), which manages the site, was ordered by magistrates last week to pay £28,184 – comprising £20,000 in fines, £8,169 in costs and a £15 victim surcharge.

What the contractor didn’t know was that a crucial gas flare alarm system relied on that power supply to mitigate excessive emissions.

The incident was caused by an error made by a contractor which was restoring the site – which had not been used for landfill since 2004, and was covered with a clay cap and restoration soils – for agricultural use.

The work involved the demolition of on-site buildings, and so the power supply was cut off in May 2008 to allow the work to be completed safely.

However, what the contractor didn’t know was that a crucial gas flare alarm system relied on that power supply to mitigate excessive emissions.

The system – which WRG must provide under its environmental permit – consists of a large number of wells that draw landfill gas out of the site and pump it to a flare. The flare burns the potentially harmful gas and converts methane to CO2. An alarm system is activated if there is a fault with the flare.

Excessive releases

After this point, the gas flare failed to function, meaning there was no gas extraction across the landfill, and the lack of power supply to the alarm meant that excessive releases of methane and CO2 were not detected for up to two days.

The Environment Agency says the reason for the breakdown of the flare has not been established, but WRG failed to install a back-up alarm and did not follow procedures for the maintenance, upkeep and monitoring of the system.

Norton Rose head of environment, safety and planning Caroline May says engineers could “get caught in a chain of causation”, such as that seen in BP’s Deepwater Horizon oil spill.

In this case, the fault lay with the site operator rather than the engineers. But law firm Norton Rose head of environment, safety and planning Caroline May says engineers could “get caught in a chain of causation”, such as that seen in the recent inquiry into BP’s Deepwater Horizon oil spill.

The inquiry into that disaster found that a series of specific engineering mistakes – including a flawed design and testing of the cement slurry used to seal the bottom of the well and an ineffective response to the blowout once it began – were partially responsible for the event. (NCE 6 January)

In the Hermitage Landfill case, the safety survey was done in isolation, says May. Although the survey recognised the need to cut off power supply to the buildings that would be demolished, it failed to take into account the existence of the alarm system. The operator knew about the latent risk of gas emissions, but failed to communicate this to the contractor.

“Make thorough enquiries yourself”

“The message for engineers going on site is to make thorough enquiries yourself, particularly where the site has historically been used for industrial purposes,” says May.

She warns that eagerness to win work in the current economic climate could lead engineers to accept a risk assessment from an operator.

This would be a mistake, she says, and contractors should always carry out their own assessments – or put themselves at risk. “What they should not do is overlook their risk profile,” she says. “Don’t get caught in a chain of causation.”

Have your say

You must sign in to make a comment.

Please remember that the submission of any material is governed by our Terms and Conditions and by submitting material you confirm your agreement to these Terms and Conditions. Please note comments made online may also be published in the print edition of New Civil Engineer. Links may be included in your comments but HTML is not permitted.