Ground and Project Consultants Ltd was commissioned to carry out a due diligence audit as to the adequacy of major remediation works at a former gas works in Greater Manchester.
Our role was to assess the appropriateness of the planned remediation in the context of its past uses and legacy of contamination and the proposed commercial end use and to assess whether the remediation works carried out met the remedial objectives set out.
Typical contaminants of concern included:
- Coal Tars: these contain a wide range of organic chemicals
- Metals and metal compounds
- Other Inorganic chemicals
The local authority approved a planning application at the site for ‘remediation and associated works to prepare land for future development’.
The works aimed at dealing with the contaminants in two main ways:
- Removing source materials
- Modifying and immobilising contaminated soils.
Various remediation activities were carried out as follows:
- Solidification/ Stabilisation of Gasholders:
- Reduced Permeability Zone:
- Filling of Voids
- ‘Clean’ Areas: These were excavated and tested against the validation criteria. The soils improved where necessary, crushed and screened and re-used on site.
- Cover system: a cover system of clean soils was deployed at site
- Groundwater and Multi-Phase Extraction
Our review concluded that:
- The remediation project was carried out to best practice standards, including appropriate liaison with the regulators.
- The remediation Strategy developed was appropriate to the legacy of the sites past use and its intended end-use.
- The remedial works were carried out largely in accordance with this strategy with appropriate regulatory liaison.
- It was highly unlikely that occupation and use of the proposed commercial development at site will pose any significant risk to end-users.