Context

Much of the M4 suffers from heavy congestion, often in excess of 130,000 vehicles per day. Improvement of the M4 to a smart motorway will help to relieve this congestion by permanently converting the hard shoulder to a running lane and using technology to monitor traffic flow. At 32 miles, this is the longest smart motorway project in England to date. 

The redeveloped motorway will provide much needed additional road user capacity, ensure faster and safer journey times, and also facilitate economic growth within the region. SDS was asked to ensure any surface run-off, that is contaminated by pollutant spills from the carriageways, is prevented from entering the natural surroundings.

Surface water pollution mitigation

SDS introduced an environmentally safe surface water storage and drainage solution within the existing structure of filter drains.

The scheme design includes replacement of the existing drainage system where required and additional storage within the drainage system to maintain current discharge rates to outfalls.

Since the scheme involves minimal additional impermeable areas, and discharges will essentially be limited to current rates, the adopted mitigation measures will ensure that any impacts on the water environment, in terms of surface – and groundwater quality, drainage and flood risk, will be negligible.

Products supplied

Weholite chambers were prepared pre-formed with an orifice plate and penstock arrangement and delivered from the company's South Wales factory. Weholite is a BBA-certified pipework and chamber system used for surface water management and pollution mitigation.

Client feedback

"The Health & Safety aspect of the Weholite system has been a huge benefit. Since the chambers were supplied pre-formed with an orifice plate and penstock arrangement, there was no need for site gangs to provide formwork onsite in the trench. Due to their light weight, the units could be easily handled without the requirement for specialist lifting plans, again reducing time and risk within the trench. By using Weholite, the first system has been installed in less than three days, shaving around two-and-a-half months off the programme and delivering potentially significant commercial savings."
– Glenn Boyd, Verge Manager, Balfour Beatty