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Contaminated Land Environmental Services Consultants Consultancy Planning Application

Contaminated Land Assessment 

We produce contaminated land assessment reports for our clients to support various planning applications and due diligence associated with land purchases. Due to the increasing number of brownfield developments and risks associated with purchasing land, regulators commonly request a contaminated land survey. The four stages of the contaminated land assessment we can assist you with are listed below.

Phase 1 Land Contamination Assessment 

 The purpose of a Phase 1 Land Contamination Assessment or Preliminary Risk Assessment (PRA) is to establish the previous uses of the land under consideration or land nearby or adjacent to it, and to identify potential sources of contamination, receptors and pathways. During a phase 1 Land contamination assessment, we identify all past uses of the site as well as adjacent or nearby sites, since pollutants have the potential to travel away from the source, depending on the geology, groundwater and surface water of the area. 

Phase 1 Assessment typically contains a: 

  • Desktop Study- A desktop study comprises a search of available environmental information and historical maps, which can be used to identify changes in land usage from old maps, trade directories and other publicly available historical records, to determine the physical characteristics of the site and to identify the likelihood of contamination. It also includes information on the general characteristics of the site including details of the geological setting.
  • Site Walkover – The purpose of a site walkover is to identify pollution linkages that are not obvious from the desk study. It helps to locate potential problem areas on the ground as Contamination of soil, groundwater and building fabrics all impart valuable visual information and to identify areas that could require detailed sampling.
  • Conceptual Site Model (CSM)-  The CSM is a written and diagrammatical summary of the environmental processes on a site and its surrounding area, the potentially significant sources of contamination, pathways through which contaminants can travel, and receptors that eventually could be harmed. We provide an outline conceptual site model based on the findings of a desktop study and site walkover which will characterise all actual or potential pollutant linkages. This basis can be used for any subsequent work undertaken such as intrusive investigations, risk assessment etc and also set out any necessary remediation works required as part of a subsequent Phase II assessment.
  • Risk Assessment- The final part of the Land Contamination Assessment is then the Risk Assessment and Conclusions derived from the conceptual site model and addresses each potential source, pathway and receptor in turn and indicates, if there is any, what the risk of contamination is.

 

Phase 2 Land Contamination Assessment 

 A Phase 2 assessment consists of an intrusive site investigation together with quantitative risk assessment. It is only required if deemed necessary as per the Phase 1 Land Contamination Assessment or to accord with any conditions the Local Planning Authority have attached to the planning approval. The purpose of a Phase 2 Land Contamination Assessment is to provide a subsequent remediation strategy for contaminated land and a verification report will also be provided.  

A phase 2 assessment contains intrusive investigations /quantitative risk assessment. This is the first part of a Phase 2 assessment. This site investigation procedure involves specialist technical knowledge and is carried out by competent and experienced personnel in accordance with CLR11 and British Standard ‘BS10175:2011 Investigation of potentially contaminated sites – Code of practice’. The findings in Phase 1 are hereby refined and potential contaminant-pathway-receptor pollutant linkages at the site are confirmed. The data obtained is in turn used to make a decision as to whether the site is potentially harmful and will indicate whether any remedial works are required to mitigate any risks from contamination that may be present. In certain situations, the process can also be undertaken in phases so that resources can be targeted at the areas that are most likely to be contaminated. The separate phases may be submitted individually as separate reports or as one combined report.

Phase 3 Land Contamination Assessment 

 Remediation is the act of rendering a site ‘fit for purpose’ under the National Planning Policy Framework (NPPF). it’s taking previously developed land and making it suitable for redevelopment, in its many forms. The term remediation covers many activities and even more solutions and is generally only applicable to land development projects. 

 Remediation Strategy

The remediation phase is in two parts:

  1. The Options Appraisal identifies and evaluates options, develops a remediation strategy, and include health and safety issues; and
  2. The ‘Remediation Strategy’ is a document detailing the objectives, methodology and procedures of the proposed remediation works.

The Remediation Strategy section also contains details on how to validate the remedial works so that all remedial objectives are met and should be approved by all relevant bodies before any remediation work starts. An options appraisal of feasible remediation options is also performed on all Phase 2 assessments. 

The range of investigation techniques that AVAL Group Ltd offers include: 

  • Bioremediation: Bacteria and other organisms will decompose some contaminants. By controlling the soil conditions, for example by adding fertilisers, water and air, these natural processes can be accelerated and the soils remediated.
  • Chemical treatment: By adding certain chemicals to the soil it is possible to chemically alter some contaminants so they become less toxic.​
  • Barrier systems: These tend to comprise the installation of a vertical containment system that effectively seals off the contaminated source and limits migration either off site or to other parts of the site.​
  • Monitored natural attenuation: Natural processes, such as dilution, dispersion, volatilisation, biodegradation, etc, will act to reduce the concentrations of some contaminants in the soil and groundwater.​
  • Thermal desorption: Certain soil types can be passed through a thermal processor in order to remove organic contaminants.​
  • Soil stabilisation: By the addition of certain chemicals to contaminated soils, the contaminants can be stabilised so that the soils can be reused.​
  • Groundwater treatment: A variety of technologies exist which can range from physically pumping out the groundwater and treating it, to introducing chemicals through boreholes to treat the contamination in-situ.​

We work with specialist remediation contractors to implement and we verify the remediation works, as appropriate.  

Phase 4 Land Contamination Assessment 

 Following the remediation of the contaminated land, there is a possibility that the Local Authority and or the Environment Agency will require verification that remediation has been completed. AVAL Group Ltd will prepare a verification report to meet the request and will compile all supporting documents outlining the process used. The report contains:

  1. A summary of the works carried out and the risks that have been managed;
  2. Validation sampling of any imported soils, including details of the source of material and appropriate analysis;
  3. All laboratory and in-situ test results and, if applicable, monitoring results for groundwater and ground gas;
  4. Photographic and other media records;
  5. Certification of any gas protection measures installed in individual buildings;
  6. Waste management and disposal documentation (‘Duty of Care’); and
  7. Confirmation that the remediation objectives have been met.