Table of Contents
Context
Chapter 17 of Volume 2 of the PEIR presents the preliminary assessment of effects on land quality with respect to soils and geology.
The geology of the Main Application Site comprises made ground, Dry Valley, Head Deposits and Clay with Flint overlying Chalk bedrock. The Wigmore Valley Park area and parts of the existing airport of the Main Application Site also comprise the former Eaton Green landfill. The former landfill was operated by Luton Borough Council between 1937 and 1978, although other records show it was still in use in the 1990s.
An extensive ground investigation has been completed to characterise the material within the former landfill and understand the risk of contamination. Preliminary findings indicate the former landfill contains a variety of contaminants, including heavy metals, chlorinated solvents and inorganic compounds, and presents a source of landfill gases. At present in its current state, the contamination levels are not to the extent that they would pose a significant pollution risk to human health or the water environment.
On the basis of a desktop review of historical mapping, previous site reports, relevant geological maps, regulatory body records, ground investigation data and site walkovers, other potential on-site and off-site contaminative sources have also been identified. Beside the former landfill, these include, car parking areas, a former scrap yard, airport activities, motor works and other industrial uses within the site and the surrounding area and areas of likely made ground. These potential sources are associated with contaminants such as hydrocarbons, heavy metals, asbestos containing materials and ground gases. The airport also had a significant role in World War II and the Main Application Site is, therefore, associated with the risk of unexploded ordnance (UXO).
Mitigation measures
Construction of the Proposed Development will disturb the landfill and therefore, a range of measures to minimise risks associated with land contamination and ground gases are proposed. Whilst these measures would be implemented during construction, they would also minimise risks during operation. The proposed measures include:
- measures proposed to be implemented by the construction contractors to manage risks associated with contamination and potential UXO are set out within the Draft CoCP. These include good construction site practices, site briefings, and compliance with legislation;
- a remediation strategy has been prepared (refer to Appendix 17.5 of Volume 3 of the PEIR), setting out details of how remediation would be undertaken and the remediation objectives to be achieved. Prior to the start of construction, the remediation contractor would apply to the Environment Agency for an environmental permit to reuse material from the former landfill; and
- a number of measures have been embedded within the design to minimise risks associated with ground contamination, ground gas and settlement during construction on the former landfill which will minimise risks during the operational period. For example:
- the location, orientation and depth of excavation into the landfill for the development platforms has been designed to reduce the amount of landfill material that will require excavation;
- all buildings present within the area of the former landfill would have ground gas management measures, to prevent migration of gases into structures;
- a perimeter ground gas control system would be installed to prevent off-site migration of ground gases to adjacent land uses;
- the geotechnical design will take into account issues associated with building on the former landfill, including ground stability, settlement and integrity, to ensure they do not impact the Proposed Development. Measures being considered to address these issues include use of ground improvement techniques, surcharging and flexible pavement;
- service connections would be modified to accommodate the likelihood of future settlement of the landfill and reduce the risk of damage to services; and
- a material cover system is proposed across the area of the former landfill to prevent contact of people with contamination.
Additional measures proposed to protect and retain the existing soil resource and minimise waste and material use are summarised within agricultural land quality and farm holdings and waste and resources respectively.
Likely significant effects
Construction
A preliminary assessment of risks to human health from existing ground contamination sources has been completed. During construction, with mitigation in place as described above, these risks are not likely to be significant. Furthermore, the Proposed Development would provide a beneficial effect to adjacent site users and properties by removing some contaminated soils and replacing these with treated materials which do not present a risk to human health, or the environment.
Operation
A preliminary assessment of risks to human health during the operation of the Proposed Development has been undertaken, considering the risk of contact with contaminated materials and the migration of ground gas into buildings. With mitigation embedded within the design, as described above, the potential risks can be managed effectively, and no significant effects are likely.
Completing the assessment
Further engagement with the Environment Agency and local authorities will be undertaken to complete the assessment, the results of which will be presented in the ES. This will include discussion of the detailed risk assessments and remediation strategy to agree the conclusions and remediation objectives, obtain agreement to a proposed gas and groundwater monitoring programme which will add to the baseline data and agree in principle the environmental permitting principles for the reuse of landfill materials.
Documents
PEIR Chapter 17 : Click Here
Figures
17.1 Baseline Conditions - Areas of Proposed Development : Click Here
17.2 Potential Sources of Contamination : Click Here
Appendices
17.1 Preliminary Risk Assessment of Land Contamination : Click Here
17.2 Land Contamination Generic Quantitative Risk Assessment : Click Here
17.3 Detailed Quantitative Risk Assessment - Human Health : Click Here
17.4 Detailed Quantitative Risk Assessment - Controlled Waters : Click Here
17.5 Remediation Strategy : Click Here