G&J design remedial strategies for a broad range of sites that have their own unique challenges, to ensure the most cost-effective and sustainable solution. Our aim is to maximize the re-use of soils on the site of origin (with or without treatment) and avoid off-site disposal and all the associated costs and environmental implications. The need for remediation is usually established through a Phase II Site Investigation and subsequent contaminated land risk assessment, and is most commonly required on Brownfield sites with a known history of industrial use. However, some apparently Greenfield or low risk sites can still require remedial measures as a result of undocumented activities such as illegal waste disposal.

Remediation may simply require a development design to consider soil quality and ensure affected soils are used only in low sensitivity areas (such as beneath hardstanding) or allow for the incorporation of a barrier layer in certain areas. Where more significant soil contamination is present, remedial solutions may be required that reduce the concentration or mobility of contaminants. Common remedial techniques include:

​

• In-situ and ex-situ bioremediation

• Physical or chemical stabilisation

• Pumping and treatment of groundwater

• Free product recovery

​

Bioremediation is a common technique for soils contaminated with organic substances such as hydrocarbons, and utilizes the microorganisms that are naturally present in soil to reduce concentrations through biodegradation.  In-situ refers to treatment undertaken on soils (or water) that remains in the ground, while ex-situ refers to treatment of excavated soils. In some cases, bioremediation may simply involve the introduction of air though mechanical means (turning soils in stockpiles known as 'windrows' using an excavator) to stimulate natural biodegradation, or otherwise the process may be enhanced by the direct introduction of oxygen, organic matter or other nutrients. 

​

​Stabilisation reduces the risks posed by contaminants in soil by either introducing a chemical agent that converts them to a less harmful form or reduces their leachability, or by mixing with an additive such as cement which locks the contamination within a solidified mass and renders it immobile.   

 

Pump and treat involves the removal of groundwater from extraction wells (or sometimes from an excavation) and passing it through a treatment plant (which may include carbon filters, oil separators, air strippers etc) located at the surface, before being either discharged to a surface watercourse / sewer, or alternatively returned to ground. A similar mechanism can be used to recover Light Non-Aqueous Phase Liquids (LNAPLs), essentially free-phase hydrocarbons that float on the groundwater and present an ongoing source of contamination if not removed. Free-phase hydrocarbons removed in this way are taken off-site for recovery or disposal.

 

In some cases, more specialized remedial solutions may be required, such as soil-vapour extraction, chemical oxidation, soil washing and thermal desorption, and we can work alongside dedicated remediation technology providers to deliver the most appropriate solution.

From the placement of a simple cover of clean soil to manage low levels of contamination, to the long term remediation of a heavily contaminated industrial site, we have the expertise to design remediation works that are appropriate to the type and scale of the problem. We ensure all remedial works are completed to the required standard, provide independent verification and agree regulatory sign-off through close consultation with Local Authorities, the Environment Agency and warranty providers such as the NHBC.