WORK to turn the M4 into the longest ‘smart motorway’ in England has posed a major engineering challenge for Thames Water, with nearly 100 water mains and sewers crossing the 32-mile stretch due to be upgraded. 

There are 89 points where pipework crosses the motorway. 

Many cross bridges, which need to be rebuilt between junctions 3 (Hayes) and 12 (Theale). Others require diverting to make way for new sign gantries and sound barriers. 

Thames Water is now in discussions with Highways England, which is carrying out the motorway upgrade, to decide how much of the infrastructure will need to be changed – without interrupting services to customers.  

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Abdul Qadeer, Thames Water engineer, said: “This is set to be one of the biggest projects of its kind the company has ever taken on.

“It’s a huge challenge and it’s vital we don’t disrupt water supplies or waste water services to residents and businesses.” 

In total, there are 37 points where water mains cross the M4, plus 52 crossing places for sewers along the 32 miles of road being upgraded.  

Thames Water’s activities are expected to start around the end of the year.  

The smart motorway project aims to relieve congestion and is due to be completed in 2022. It includes converting the hard shoulder into a semi-permanent lane.