DRAINAGE PROJECT
A46 Filter Drain Recycling
Widmerpool TO Willoughby
Carnell worked in collaboration with M&R contractor Amey and the client National Highways to undertake filter drain refurbishment on the A46 between Widmerpool and Willoughby in August 2023.
Using the StoneMaster process to recycle the filter drain media in-situ, provided several carbon, safety and customer benefits over the traditional dig-out and replace method. This was enhanced by using three machines in tandem for greater speed and efficiency.
The 6,480m length of filter drain (verge and central reserve) was brought back to specification in nine night shifts, one ahead of schedule – which was used to clear overburden. By only taking away non-compliant material (24% of what was in the drain), over 600 lorry journeys were removed from the network, while the reduction of materials, haulage and waste disposal led to a reduction in CO2e emissions of almost 61 tonnes.
Using StoneMaster on the A46 to recycle the filter drain in-situ resulted in:
- Safer roads along the 3km route.
- Re-use of 3,926 tonnes of aggregate.
- 15,810 fewer HGV miles transporting materials.
- Reduction of 30,604m3 CO2e.
Added Value
Overburden (the vegetation that grows above the filter drain and in the central reserve), was removed to enable improved flow of surface water into the filter drains, to minimise standing water in the carriageway. In producing a fully functioning filter drain which will extend the life of the carriageway, StoneMaster removed a tonne of non-compliant material every 5.1 linear metres of filter drain. This is what fills the voids in the filter media, reducing the drain’s effectiveness.
With the asset returned to its optimum performance, the filter media was also reinforced using Carnell’s TRL approved StableDrain solution. This elimininates stone scatter if errant vehicles traverse the filter drain and stops HGVs from becoming embedded in the drain if they stop on top of it.
Benefits
- HGV movements in and out of traffic management reduced by 66%.
- Better drainage means improved safety for road users as water is effectively removed from the surface, minimising risk.
- Drain reinforced using Carnell’s TRL approved StableDrain solution to minimise stone scatter from vehicles traversing the drain.
- Using three StoneMaster machines in tandem meant just 9 overnight closures.
- Other M&R activities such as repairs to the barrier, concrete surface and carrier drain pipework, plus arboriculture were carried out in the same closure.
- Proactive maintenance of the network reduces disruption and helps our customers feel safe.
- Full closures gave best use of budget, with minimal traffic management required.
- StoneMaster also has greater outputs compared to the dig-out and replace method.
- StoneMaster supports National Highways’ Net Zero ambitions because all reusable material is returned to the drain / only noncompliant material is removed from site.
