Bespoke aggregate engineering plant helps power Careys’ robust remediation capacity

Lessening the environmental effects in the construction industry

In order to respond to the urgent need for greater sustainability on UK construction sites, the industry has devoted a fair amount of attention and resources to improving remediation practices. This is especially important in urban or industrialised areas, where a substantial proportion of sites occur on brownfield or pre-developed land, many with pre-existing structures that need to be renovated or demolished. One of the biggest challenges that these projects pose is the need to find green ways to efficiently and responsibly deal with and neutralise the effects of contaminated materials.

We must do all that is in our power to safeguard our surroundings by making sure that any by-products of construction or demolition activities – such as contaminated soil and materials that result from demolition or groundworks processes – are, to the greatest extent possible, remediated and reused, rather than sent to landfill. Just this one step alone has the power to drastically improve the construction sector’s impact on the environment.

At the forefront of the industry’s remediation efforts

At Careys, we have taken a number of steps to ensure that we are on the leading edge of the search for effective remediation initiatives and solutions. We have invested considerable time and resources to design and deploy systems and equipment that can improve our on-site remediation and recycling capabilities.

Our aggregate and soil engineering plant is one of our most impactful and far-reaching remediation investments to date. It has dramatically enhanced our ability to decontaminate and recycle vast amounts of soil and aggregates. It also gives us the ability to reduce our carbon footprint, by cutting down on vehicle movements, which are usually required to transport clean aggregates onto sites and contaminated materials off to disposal locations.

We first rolled out our custom-designed aggregate and soil engineering plant at the Ford Dagenham project in east London. Our use of the soil aggregate engineering plant on this project has been so successful that, going forward, it will form one of the centrepieces of a set of full-service, broad-ranging remediation solutions.

Careys remediation of the Ford Dagenham site

As principal contractor on the Ford Dagenham demolition and remediation project, Carey Group company, Scudder Demolition, utilised our customised aggregate and soil engineering plant. Our use of this cutting-edge equipment helped to ensure the greatest level of sustainability in the reuse of materials on this massive regeneration project, designed to remediate the site to residential development standards.

Our aggregate engineering plant, which is regulated under an environmental permit, is capable of processing 500 - 750 tonnes of materials per day, depending on input spoil type. This greatly enhances our capabilities and expedites our pace in remediating contaminated sites. As part of its bespoke design, the scalable plant is totally “plug and play” – it can be rapidly demobilised, transported and remobilised at new sites within approximately four weeks, from end-to-end. The aggregate engineering plant is Carey groups biggest single plant investment to date.

The huge Ford Dagenham site had a demolition boundary of approximately 20 hectares (the equivalent of 28 football pitches). The property contained a large number of buildings that covered 70% of the site, with unusually big (in excess of 1 hectare) and deep (7m) basements, as well as other buried obstructions.

Before commencing demolition works, we conducted additional site investigation works in order to confirm the extent of soil contamination and its effects on the groundwater. We installed over 100 monitoring wells and numerous trial pits to refine the contamination detected during the original site investigation.

Once we had identified the nature and scope of the on-site contaminants, we began demolition of the entire facility, including floor slabs, foundations and basements. This included installing 1km of sheet piles to stop groundwater ingress into the deep basements during demolition. Throughout the course of our on-site works, we used ground-penetrating radar surveys on areas of slab removal to further locate and assess any buried obstructions and pipe works.

Based on our findings, we subsequently treated chlorinated solvents in excess of 15,000 tonnes of excavated materials. We also treated up to 200m³ of solvent impact waters a day, via a combination of oil skimmers, sand filters and granulated activated carbon filters.

In addition, we dealt with oil contamination, which stemmed from two main sources, small leaks around pipes and a major historic hydrocarbon plume in the former wheel room within the shallow peat strata and within the upper terrace gravels. We treated some 50,000m3 of hydrocarbon impacted spoil, skimming 25m3 of free product.

The aggregate and soil engineering plant

Our remediation and soil engineering plant essentially has four main phases of operation:

• Oil skimming and carbon filter water treatment for hydrocarbon-impacted waters and in-situ soils
• Soil washing to remove contamination
• Screening to separate excavated spoil into size fractions
• Soil pressing to solidify the liquefied “clay/silt” fraction generated during soil washing

At Ford Dagenham, we placed soils that had been highlighted for remediation within the soils management area (SMA), and then processed them through the plant. Afterwards, we tested the materials, prior to reuse, in order to ensure contract compliance.

To ensure the maximum level of sustainability, we made certain that the water used in the plant was treated groundwater from on-site remediation works. Throughout the process, we continually monitored the water in our in-house laboratory facility and maintained the water quality by feeding it back through the water treatment facility before reusing it in the plant.

As a result of performing remediation on-site, we were able to effectively remove dozens of trucks from the roads every day – significantly decreasing transport and processing costs for our clients, improving project efficiency and keeping our carbon imprint down.

In line with the site Flood Risk Assessment the site level needed to be raised by 1.5m in order to meet Environment Agency flood guidance levels - it was still necessary for us to import approximately 350,000m³ of materials. Yet, with the help of fellow Carey Group company, Seneca Resource Recovery, we were able to bring in 90% of all the required fill for the Ford Dagenham project from other Carey Group London sites. We then remediated these materials using the soil engineering plant. By doing this, we were able to greatly reduce the amount of materials that needed to be sent to area landfills.

Careys’ in-depth remediation capabilities provide clients with a wide range of sustainability solutions

Our substantial investment in and use of the aggregate and soil engineering plant clearly illustrates Careys’ dedication to utilising innovative solutions to safeguard the environment. Due to our meticulous research and planning, we were able to successfully source, modify and employ this wash plant at Ford Dagenham, and implement a system that functioned like clockwork.

This is just one of a series of innovative and forward-thinking remediation initiatives that Careys has been utilising across our projects throughout the UK and Ireland. For example, there’s our in-house chemical testing laboratory, which we also used at Ford Dagenham. This site-based laboratory facility allows us to conduct same-day, real-time monitoring of excavated materials at all stages of remediation and processing, in order to characterise them for reuse. On the Ford Dagenham project, our partnering consultant, AAe independently operated the chemical testing lab, with further verification testing carried out by external laboratory partner, Chemtest.

Additionally, our unique self-delivery model features Carey Group companies – such as Careys Civil Engineering, Scudder Demolition, Seneca Resource Recovery, Careys Design Team and ION Environmental – working together collaboratively to deliver a full spectrum of decontamination and remediation services quickly and efficiently.

In the months and years ahead, we will continue to proactively and innovatively expand our remediation capabilities, in order to ensure that Careys provides the most vigorous remediation solutions available.