Former Chemical Works and Multiple Landfill Site, Castleford

Site name  Castleford

Development  Residential Dwellings

Details  Significant Contamination and Specialist Risk Assessment

Role  Environmental Consultants

ASL operated as geo-environmental consultants for the redevelopment of a former chemical works in Castleford.  The site is dissected by surface water features that form an island that is also part of the site.  The boundary between the site and the surface water features is formed by a discontinuous sheet pile wall.  The site comprises a former chemical works that has historically manufactured a variety of products.  The site can be generally split it into 6 areas based on their uses namely playing fields, a peninsula, an island, the main site works, drum storage area and the landfill area.  The landfill area can be subdivided into three further areas comprising a former lagoon settlement facility, a site derived waste landfill and a hazardous waste landfill.

The site has been subject to multiple phases of investigation that identified significant concentrations of contaminants of concern in soil and groundwater.  The main contaminants of concern were organic semi-volatile and volatile organic compounds (SVOC and VOC).  Of particular concern were species including chlorobenzene, 4-chloroaniline, 2,4-dinitrotolune and xylene that were identified in groundwater across large portions of the site.  However, other contaminants of concern were identified at elevated concentrations including total petroleum hydrocarbons, polycyclic aromatic hydrocarbons, pesticides, herbicides and metals.

A previous assessment of the site had identified the need for a soil and groundwater remediation in order to be protective of the surface water features bounding the site.  A variety of remediation techniques were recommended to achieve the defined remedial targets.  Due to the nature and extent of the contamination and the stringent nature of the remedial targets, the potential for success and feasibility of the proposed remedial works were not guaranteed.

ASL were contracted to completed a detailed quantitative risk assessment to further assess the potential risk to controlled waters from dissolved phase contamination in groundwater.

ASL completed a Tier 4 quantitative risk assessment to determine the potential risk to controlled waters.  Based on the findings of the Tier 4 assessment, remediation of groundwater was recommended at two exploratory locations only.  A monitoring programme was recommended as part of the development programme to confirm the conclusions of the assessment.  The assessment was issued to the Environment Agency to their approval.

The works completed by ASL comprise the following:

  • Review of previously completed reports, historical data, the site’s environmental setting and land use;
  • Detailed assessment of the contaminant source area and flow path;
  • Interpretation and quantitative assessment of results for contamination issues;
  • Design of a monitoring programme during the construction phase to validate the quantitative risk assessment.