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Under the weather

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Posted by Adam Lyons on 14th Mar 2018

Construction sites throughout history have been vulnerable to unforeseen events, be they violent storms, earthquakes, volcanic eruptions or armed attacks.

We may not have Mongols or Romans at the gates today, and, in the UK at least, the direct threat of volcanoes and earthquakes is low – but preparing for the unexpected is vital for any construction site project manager.

Weather can cause turbulence for a project, given the delays that rain, snow or wind can cause to timetables, budgets, and the health and safety of workers.

But to what extent do project managers build such contingency into their project plans? And how seriously do they take the issue?

Gavin Lawless, contracts manager at specialist engineering firm Keltbray, who is working on residential development at The Stage in east London, says weather is a vital part of his early project planning.

“Our site is circa 7000m2 and is wide open to the elements, so the impact of weather is important during all seasons,” he says. “For example, both cold and hot weather can affect how you manage large concrete pours, as it affects the chemical reaction within the concrete, so the mix may have to be tailored to suit the environment on the day. On very windy days, our cranes will be put out of action, and you need to ensure that all materials stored are made safe. The monoflex, which is solid to encapsulate a structure during demolition, may need to be cut to allow for wind to pass through, or it will act like a sail, causing a much larger issue.”

Lawless says that, before every job, he makes allowances for such delays: “We can only estimate how many days we will lose to weather. We look at daily and weekly forecasts for the area, and look for trends. On a monthly and weekly basis we will review our upcoming works and how they may be affected by the weather, and move and plan accordingly.” 

Assessing the risk

Construction management consultant Paul Netscher says it is tricky to cover all likely events.

“Risks are viewed differently by the client and the contractor,” he says, “but the contractor can’t be expected to account for risks that it could not expect. Normal weather events should be allowed for and priced by the contractor – but this is not the case for unexpected, abnormal weather. After all, how much abnormal weather should you allow for? Allowing for every event that may happen would make projects prohibitively expensive.”

Netscher also references other, non-weather factors: “Contractors operating in areas prone to power cuts should allow for these in their price. But a sudden spate of unexpected power cuts can’t be allowed for. Life is full of risks – driving a car and travelling by aeroplane bring risks. We limit these risks by choosing safer airlines and cars. We don’t stop flying or driving. We need to manage risks through the life of every project.”

He says that, ideally, risks in construction must be allocated to the party that can best control them: “Owners and clients who try to pass all the risk to their contractors will end up with many contractors declining to price their projects, and those that do adding significantly to their price to cover the additional risks they are expected to carry.”

The need to refocus

Netscher believes that project managers do not give weather the focus it deserves: “Contractors are eternally optimistic and never seem to allow for any weather-related impacts on construction projects. If you have 20 inches of rain in three months, it will almost certainly disrupt your project. But, if the average for the region is 20 inches over that period, you shouldn’t be surprised. You should have made allowance for it in your construction schedule and taken mitigating measures. It is not just the direct time lost – rain or wind can cause damage to partly completed structures that could take days or weeks to repair.”

So, how can this be mitigated? Netscher has the following advice:

  • During the bid or tender stage, project managers need to understand the expected weather conditions at the location and discuss the related issues with their client.
  • Project managers need to schedule activities in accordance with the weather, such as closing up site work ahead of expected wind or rain.
  • Different construction techniques can be put into action, such as modular construction and precasting, to keep the project on track during bad weather.
  • Put protection measures in place, such as open-cut storm drains to channel rainwater away from work areas, and secure loose materials before high winds hit.
Expert predictions

Accurate and timely weather forecasts are clearly vital. One source of these is the Met Office, which has a dedicated business and construction team that caters for construction project managers.

Steven Davey – sport, leisure, industry and infrastructure manager at the Met Office – says the organisation helps construction project managers at all phases of a build, from project planning and delivery to analysis.

“When planning, you can assess what the site conditions are likely to be using long-term averages and one-in-10-year event data,” he explains.

For project delivery, the Met Office has created a new online weather tool called VisualEyes. It offers location-specific weather alerting, with forecasts out to 14 days highlighting weather patterns of concern, and allows the customer to set specific amber and red warnings, triggering email and text alerts.

“You can set your own operational thresholds,” Davey explains. “So, when they are breached – such as the temperature falling below 2˚C, meaning concrete should not be poured – you will be alerted. You can also track the direction of travel of a storm to protect against lightning strikes, or wind at height.

“Forecasts at days eight to 14 give more of a climatological view, but we are very confident about the accuracy of forecasts up to seven days. We have recently acquired a new £97m supercomputer to improve our prediction capability, so our accuracy is constantly improving to the point where we are seen to be one of the most accurate meteorological services in the world.”

Davey says the system has been up and running for just longer than a year. He admits that there are not as many people in the construction industry who know about VisualEyes as there should be, but stresses that, when introduced to the system, “people quickly see how it can benefit construction operations management”.

The Met Office can also help with analysis with regard to proving the need to claim for downtime on contracts such as JCT, NEC3 and NEC4.

“We produce historical reports looking back over a month – showing, for example, that the project had to be delayed in May because of exceptional weather circumstances,” Davey says. “We make calculations to see if an exceptional weather event has occurred on-site, and present these as one-in-10-year figures and long-term averages. This was previously only possible with data from weather stations, but today we can be pretty much location specific, allowing for geographically representative reporting.”

Weather alerts

Ulrik Branner, chief executive at construction management software group GenieBelt, says weather-alert technology can be the “tap on the shoulder” project managers need.

“Project managers may be focused on weather at the start of the project, looking at all the statistics, but it often slips down the priority list,” he says. “A construction site is a living organism, and soon a project manager is faced with 600 things to do. So, mistakes happen, and after a storm you find scaffolding has been blown away because it has not been secured.”

GenieBelt has devised new technology that communicates with project managers about weather changes and what strategic actions to take.

“We inform them that a storm is coming next Monday, but we also know that this is when they have scheduled crane work – or that the temperature is set to drop to -12°C when they are pouring concrete,” Branner says. “Our system lets them know in advance through noise alerts on their smartphones to prepare and clear the site of loose building materials, or to reschedule pouring. So, we combine strategic and site data with weather data and inform on what needs to change. We believe you can reduce the cost of a build by nearly five per cent if you reduce errors, and weather delays are part of that.”

It is not just cost. Branner says the health and safety of workers will also benefit: “Think of the impact and toll on the human body of working in bad weather. Weather technology helps protect workers.”

Keltbray’s Lawless agrees: “The weather rarely changes too much from what is expected season to season, but what has changed is the focus on the health of workers and what effects the weather may have on our guys. As a wide-open site, you could have localised areas where dust gets kicked up. You need to plan for this and ensure there is a strict dust-control regime in place. The use of dust monitors and wind gauges ensures that we can keep an eye on these environmental risks.”

Of those who work outdoors, construction workers account for the largest proportion of skin cancer cases, with 44 per cent of deaths. Lawless has signed up to a new research project involving 10 Keltbray employees at The Stage, Heriot-Watt University and the Institute of Occupational Medicine. The workers are using a smartphone app that sends them text messages reminding them to cover up and protect their skin if heat and UV levels rise.

“The workers have also provided blood samples to measure vitamin D levels. We want them to maximise the benefits of that in summer and ensure that, in winter, they maintain healthy muscle and bone strength,” says Lawless. “We don’t want their health or well-being to be affected.”

Queensferry Crossing

The Met Office’s work on the new Queensferry Crossing road bridge in Scotland is an example of how weather forecasting can help a build. Rain, strong winds, icy conditions and the ‘haar’ fog can create tricky working conditions, explains the Met Office’s Steven Davey.

Builder Forth Crossing Bridge Constructors (FCBC) approached the Met Office to help mitigate the impact of the weather on the construction plan and build.

“In the pre-construction phase, we conducted a study of the proposed bridge site, using our Virtual Met Mast, a site-specific wind-prediction solution, together with a general climate assessment from the nearby Edinburgh Gogarbank meteorological observation site,” Davey explains.

“We gathered information on the climate of the build site, and identified times of day when winds would potentially be at their highest and lowest speeds, and the times of year when wind shear would be at its greatest and least. We also provided a rainfall analysis of the build site. This enabled the construction design team to evaluate and refine its structural designs to best mitigate any impact of the weather, and the project management team to assess schedules for the construction phase.”

During the build phase, FCBC received a five-day site-specific forecast giving an hourly breakdown on the first day. They used the Met Office’s web-based planning tools to plan weather-dependent tasks.

“The team was able to optimise when it hired large and expensive equipment,” Davey adds. “They were also notified via alerts of changes to wind speed or direction that could cause problems on-site.”


David Craik is a business journalist and editor

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