Remediation

Ground water treatment

Apart from being a requirement for regulatory compliance and environmental protection, the treatment of groundwater is very often an integral part of the remediation and regeneration of brownfield land. Cognition Land and Water has many years of experience and innovation in this area and we have developed our in-house capability, resources and expertise to include a wide range of techniques and technologies for the treatment and discharge or disposal of groundwater, surface water and tank contents. These include:

• pump and treat
• insitu treatment
• extraction, treatment and disposal
• chemical oxidation
• air sparging
• vapour extraction
• novel PFAS treatment technology
• unique FabEx product removal system
• suspended solids control

Permeable Reactive Barriers

A Permeable Reactive Barrier (PRB) is a treatment zone of reactive material that is built below ground to clean up polluted groundwater. The reactive zone may be installed as a below-ground wall to intercept a migrating plume of contaminated groundwater. Alternatively, the contamination can be funnelled by low permeability barriers (e.g., slurry walls) to a gate or vessel containing the reactive media - the funnel and gate method. The reactive media is selected to absorb or adsorb the pollutants from the groundwater or to convert harmful chemicals to harmless by-products.

 Cleaning groundwater with a PRB may take many years as the time taken depends on the amount of pollution present in the groundwater and how fast the groundwater moves through the PRB. Despite this, there are several advantages of using a PRB to remediate contaminated groundwater:

• The installation is beneath ground preventing human contact with the contamination
• Low operating and maintenance costs
• No energy requirement as the system relies on natural groundwater flows
• No pumps, moving parts or associated noise
• Invisible after installation
• Allows continued use of the site after installation

 Cognition Land and Water has successfully installed PRBs at more than 100 sites.

PFAS Treatment

PFAS (Perfluorinated alkylated substances) are a group of man-made substances used in many industrial and consumer products such as carpeting, clothing, fire-fighting foams, cooking pans, coatings, etc. because of their resistant to water, oil and heat.  These chemicals are highly persistent, very mobile in soil and groundwater, and resist degradation in the environment.  They bioaccumulate and PFOA - one of the primary compounds within the PFAS group - is believed to be in the blood of virtually every living creature on the planet… including 99% of humans.  These ‘forever chemicals’ have been linked to adverse health effects such as low birth weight, delayed puberty onset, elevated cholesterol levels and reduced immunologic responses to vaccination.  At Cognition Land and Water, we have been closely monitoring the progress of knowledge around these new and emerging chemicals and have been actively involved in the design and implementation of remediation strategies for a number of key sites including former airfields and fire fighting facilities.  We are also partnering with the Australian developer of a novel and innovative water treatment process that removes all detectable traces of PFAS from treated water at high throughput rates, at low cost and without the need for costly and limited capacity reagents, catalysts or filters.  In our aim to be at the forefront of our industry, Cognition is actively funding the production of CIRIA best practice guidance on the assessment and remediation of PFAS impacts as well as being a member of the Project Steering Group.

Asbestos in Soils

Asbestos in soils has been a contentious and problematic issue on development sites throughout the UK for many years. Without correct management of the demolition of previous buildings or the placement of fill or made ground that contains asbestos fragments, cleaning up the problem can be costly, time consuming and fraught with risk. But this doesn’t have to be the case…

 At Cognition Land and Water, we have a longstanding track record of managing and remediating issues associated with asbestos in soils. Careful materials management, selective screening, hand picking, processing and treatment of soils can remove the bulk of the asbestos. Once this much smaller volume of highly concentrated asbestos has been removed from site and disposed at a suitably licensed facility, the residual soils can be reused within the works. If placed in a distinct and recorded location, beneath a clean cover system, there is no risk to future site users or the local environment and the development can progress without undue cost, programme of regulatory compliance issues.

Bioremediation

From bench and field trials in the challenging conditions and climate of Kuwait to scores of successful bioremediation projects in the UK, Cognition Land and Water has an enviable track record in the successful and cost-effective remediation of hydrocarbon impacted sites using bioremediation technologies. We have funded and undertaken academic research and trials to ensure that the additives we use and the temperature and moisture condition we maintain in our works result in the most aggressive conditions for the breakdown of hydrocarbons in the least time possible.

On our projects, we regularly treat excavated and processed hydrocarbon-impacted soils ex-situ using bio additives. The soils are treated using a number of additives including HCR, Bio SRO2, PGA, Bio nutrient, cultured indigenous bacteria and Skyhawk Hydroeater. Cultivated indigenous bacteria and ligninolytic fungi may also be used to supplement treatment processes and Oxygen Release Compound (ORC) Granules may be used for extended aerobic bioremediation of the hydrocarbons.

 Where it is uneconomical or not possible to remove material for bioremediation, we have also carried out in-situ bioremediation. These methods are implemented through boreholes, forming trenches or in-situ bio piles and can prove very effective in the right circumstances.

Invasive Species

The main invasive species found on marginal land include Japanese Knotweed, Giant Hogweed, Himalayan Balsam and Rhododendron Ponticum. They are all highly regulated and allowing them to spread off your land can be a criminal offence. Although there is no obligation to remove from land you own, these species spread quickly, out-compete native plants, and can cause serious damage to structures, pavements and drainage infrastructure.

 Working with specialist ecologists in the identification and survey of invasive species, Cognition Land and Water generally uses one or a number of the following methods to eradicate invasive species on our projects:

• Herbicide treatment
• Excavation and on-site treatment and burial
• Off-site disposal
• In-ground barriers to avoid reinfection from adjacent land.

Encapsulation & Stabilisation

Soil Stabilisation involves the introduction of specially formulated cementitious or liquid solutions directly into or onto the ground through the use of purpose built injection augers or dosing at the surface followed by rotavation and compaction. The system is designed to achieve reduced permeability and/or increased strength within the soil mass to improve the physical properties of soils. However, it also has the added benefit of ‘locking in’ leachable contaminants, thereby providing a very effective remediation solution.

 This technique is a cost effective alternative to importing aggregates for both temporary and permanent works. Cognition Land and Water was one of the first ground engineering contractors to introduce to the UK the notion of cement stabilisation of site arisings to create pile mats in the early 2000s. We now use this approach on over 90% of our sites resulting in a far more sustainable, cost-effective and quicker working platform than the disposal of site arisings and the import of aggregates.

 In-ground soil stabilisation can be used to form highly efficient cut off walls within or around contaminated sites without needing to dispose of large volumes of contaminated spoil. Cognition has used this technique on many sites to great effect.

Validation and Verification

Scrupulous record-keeping and collating site verification/ validation/ completion report data from the start of the project (rather than upon completion as is oftentimes done by others) is a distinct approach taken by Cognition Land and Water.  We have learnt through experience that the alternative approach (collating the required information at the completion of the project) is stressful, fraught with difficulties, and less likely to achieve a high quality Verification Report required for discharge of planning conditions, surrender of an environmental permit, confirmation of the completion of the works, and settlement of final payments. 

 This is why we have put in place comprehensive systems and procedures to ensure we maintain accurate and up-to-date records of site works from project commencement and collate those records in one location in our project folders from the outset to make the compiling of the final verification/ validation/ completion report a straightforward and painless process.

Site Investigation

Cognition Land and Water is not a site investigation contractor and we do not regularly carry out site investigations as a single service on a project.  However, through the vast experience and track record of our professional team, including several who have worked within ground investigation contractors and consultants for many years, we are adept at planning, specifying and managing site investigations for projects where we have been commissioned to carry out our ground engineering and/or remediation contracting services.  This may include additional desk study research, supplementary ground investigation following gap analysis, ground investigation to finalise detailed design, additional investigation to refine our approach or solution to a project, installation of additional gas/ groundwater monitoring wells, or investigations into unforeseen ground conditions during a project.

 Our in-house staff and plant resources makes the execution of ground investigations cost effective and rapid for our clients.  Strong relationships with our network of specialist ground investigation contractors means that we can bring in these specialist services on larger investigations using a wide variety of techniques and technologies.

Fabex-free product removal

Cognition Land and Water offers an innovative solution for the remediation of free phase oil contamination of groundwater. Having already achieved great success in dealing with contaminated sites across much the USA, Cognition is unique in offering the system to the UK market.

Traditional remedial techniques, such as pump and treat, are often costly and inefficient in recovering free product. Based on extensive experience addressing petroleum and chemical spills, we can deploy the FabEx system to recover both light and dense non aqueous phase contaminants (LNAPL and DNAPL), also known as free-phase product.

 The simple but highly effective NAPL Fabric Extraction Technique - FabEx - utilises an oleophilic/ hydrophobic fabric capable of adsorbing the product with a 99% recovery efficiency. The fabric is conveyed in a continuous loop into the well to intercept the oil-water interface.  As the fabric travels through the interface, product is adsorbed. The adsorbed product is then removed in a specially designed desorption unit and the recovered oil collected in a storage drum or tank for disposal or recycling.

 There are many advantages of the system over conventional groundwater treatment or product removal systems but the key benefits include:

• Small footprint is perfect for operational or space restricted sites
• Eliminates the need to extract/ treat/ process large volumes of groundwater
• Minimises or eliminates disposal costs
• No requirements for groundwater permits
• Recovery is not influenced by fluctuating water table
• Light/dense Non Aqueous Phase Liquids (NAPL) recovery at highly impressive speeds
• System can be deployed in wells of varying diameters (as small as 50mm) and in boreholes at depths of up to 60m
• Recovery efficiency with 99% product-water ratio
• Reduces O & M costs by nearly 70%
• Optional remote operation
• Low power usage and can be combined with solar and wind power units

Material Management

At Cognition Land and Water, the key driver in establishing a pragmatic and cost-effective remediation strategy for a brownfield site is most often the minimisation of off-site disposal and onsite reuse of site won soils. As an example on our Royal Wharf development in East London, we achieved 99.5% soil reuse on the project with large sustainability, environmental, cost and programme benefits. High quality materials management and effective processing, treatment and remediation of impacted soils is fundamental in achieving this enviable outcome.