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Balfour Beatty on behalf of Highways England appoints SDS to prevent the contamination of surface water runoff.


Much of the M4 currently 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 runoff, that is contaminated by pollutant spills from the carriageways, is prevented from entering the natural surroundings.

M4 Smart Motorway


SDS introduced within the existing structure of filter drains, an environmentally safe surface water storage and drainage solution. 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. The existing central reservation drainage system will be replaced with surface water channels or linear drains, and some sections of the verge drainage will also be replaced with new linear drains.

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 ground – water quality, drainage and flood risk, will be negligible.

Image kindly supplied by Balfour Beatty


The product’s versatile nature and ability to be delivered from its South Wales factory in a timely manner, in unique sections of pipework, ensured that this project could be delivered on time.

The client also recognised the benefits of the Weholite product’s light weight, proven durability, resistance to abrasion and toleration of ground movements.

"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 at Balfour Beatty

Download the full case study here

SDS Weholite Pipes


SDS Weholite spirally wound pipe systems are manufactured from corrosion-resistant HDPE, providing a light weight, engineered solution with superior loading capacity that is chemically inert and provides a 120-year life.

Weholite can be used in a variety of applications from simple road or rail culverts to more demanding inter-process pipework on sewerage treatment plants and for offsite build components.

Weholite pipes can also be used for hydroelectric pipelines and intake structures, anaerobic digestion and air vent systems , and as storage, contact and inter-process pipework for drinking water applications.


Discover how the SDS portfolio can benefit your development and get in touch now.