How new soil treatment is helping to divert excavated soil from landfill

Written by: Andy Bareham | Published:
Part of the SMR tip and take recycling process

New soil treatment and stabilisation technology means excavated spoil can be recycled and diverted from landfill. Andy Bareham, technical manager at SMRUK, explains.

In the past, excavated spoil from utility trench reinstatements and construction site excavations would traditionally have been sent to landfill. Now, in today’s cost-conscious environment, where recycling and sustainability are a priority, contractors, local authorities and other landscaping-related sectors are increasingly seeking solutions to reduce escalating operational and landfill costs.

Recent technological advancements have resulted in a new generation of dry-mix powder additives being formulated, which when added to excavated spoil create a ‘structural material for reinstatement’, commonly known as SMR. This transforms spoil in minutes into a high-quality, high-performance sub-base replacement.

Typically around 2% by volume of the SMR dry-mix powder additive is combined with the extracted spoil, creating a stable sub-base and backfill material. The process not only removes excess moisture from the spoil, it also stabilises the material for optimum compaction, bonding the sub-soil particles together, increasing density and strengthening the material by as much as 600%. This reinstatement material repeatedly outperforms traditional materials such as Type 1 GSB.

To date, using this technology, more than two million tonnes of spoil has been transformed into viable reinstatement material, repurposing and therefore recycling it. However, diverting the spoil itself from landfill is only part of the picture.

Transportation is another key factor and a big producer of carbon dioxide through emissions, with the estimated related saving around 7,000 tonnes of CO2. This is calculated on the basis of a 10-tonne lorry on an average 40-mile round trip to transport the spoil to landfill creating 35kg of CO2.

Fulfilling its recycling potential

Each year thousands of kilometres of roads and footpaths have to be reinstated following utility repairs. The UK national gas agencies have an estimated 272,000km of gas distribution pipes, with a further 131,000km belonging to the National Grid.

Then there is approaching one million kilometres of power lines and cables servicing the UK (around half of these being buried) which they need regular attention and repair. There is also an extensive network of water and waste pipes, with recent reports stating that some 350,000km are designated for replacement. So if just 5% of services are replaced or repaired each year, that’s another 17,500km.

These figures don’t take into account newbuild or any of the reinstatement projects implemented by telecommunications or cable companies, making the UK market potential for recycling as much of the excavated spoil from any of these projects sound practical and economic sense.

Using this enhanced material provides real trench cohesion by ‘grabbing’ the trench walls, significantly reducing the block and beam effect so often seen in conventional reinstatements. Because the chemical transformation process commences within minutes, a wearing course can be laid soon after, so the complete operation can often be done within a single visit – an extremely attractive financial proposition from a utility industry perspective.

The traditional solution is to remove the excavated spoil to landfill, returning often a day or so later and backfill using appropriate reinstatement material. This allows a further few days before another crew finally return to add a wearing course. A costly, disruptive and time-consuming process. With this process there is no need for a base course, only requiring a wearing course, making additional cost savings.

The benefits to the recycling sector are numerous and still increasing. If the UK were to increase its use of SMR by just a few per cent over the next few years, the environmental and financial savings would be enormous. Go beyond the UK and that becomes a whole new ball game.

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