Erection of Three Dwellings, Elm High Road, Emneth, Wisbech, Norfolk, PE14
Case Study Reference: CS16-04-08
Planning Authority: King's Lynn and West Norfolk Borough Council
Planning Reference: 17/02386/O and 17/02163/F
Synopsis:
In order to demonstrate that after the development the site could not be classified as ‘contaminated land’ under Part 2A of the Environmental Protection Act a Phase I desk study report was required to support the application for residential redevelopment of the site.
A desk study determines what issues relating to historical contamination may affect the site, this is undertaken by reviewing the site history using a combination of O.S. maps, aerial, plates and street level imagery, a review of data held by regulatory bodies (Environment Agency, local authority, BGS etc.) as well as a site walkover survey.
The history of the site and surrounds were researched using a combination of Ordnance 
Survey (O.S.) maps, street level imagery and aerial plates, this revealed the site was initially (1886) undeveloped with a canal on the western boundary of the site. The canal was in-filled between 1950 and 1959.
Street level imagery of the site confirmed the site comprised of a parcel of open land.
The planning history of the site was reviewed as part of the desk based research and reports associated with any previous application were located and studied, an application was made in 2004 for the continued use of the site as a home improvement centre, which was refused.
The published geological maps identified the site being in an area where the drift geology comprised of Tidal Flat deposits. the solid geology is given as the Ampthill Clay Formation (mudstone) of the Oxfordian epoch.
Data provided by the Coal Authority indicated that the site is not within a “Development High Risk Area”.
A review of the BGS borehole database indicated no boreholes were available in close proximity to the site.
Data provided by regulatory bodies confirmed the presence of a can con the western b
oundary of the site as well as a number of ponds and a heap within 250m. Data from the Environment Agency indicated the in-filled canal is a landfill (Wisbech Landfill) which accepted a variety of waste streams.
The sensitivity of controlled waters was undertaken to determine if the site posed a risk to the nearby controlled waters, this concluded that as the controlled waters was of low risk and no further assessment was warranted.
A literature review was undertaken regarding the Wisbech Canal landfill and a desk study report summarising the works undertaken on the canal, dated April 2010 was sourced and reviewed. This concluded that there were ‘no significant risks from landfill gases or exposure to the landfill soils’
On completion of the desk based research a site reconnaissance visit was undertaken, this
confirmed the site comprised of open land with the area of the in-filled landfill/canal being roughly overgrown.
Once the walkover survey was completed a qualitative risk assessment was undertaken on the potential sources of contamination identified in the desk study report in order to determine if any warranted further investigation, this concluded that the potential for made ground to be present on the site as well as the materials in the in-filled canal/landfill posed a potential risk and further works were required to assess this.
The proposed works comprised of a non-targeted sampling grids based on a 10m grid as well as the option for either ground gas monitoring or the incorporation of gas protection measure sin lieu of ground gas monitoring.
The report was submitted to support the application, the recommendations of the report were accepted and planning granted.
The site investigation was undertaken in December 2016 once the client confirmed that gas protection measures were to be incorporated into the building design. The site investigation followed the guidance in the site investigation report.
As part of the investigation the boundary of the in-filled canal/landfill was determined. Samples from both areas were taken and subject to chemical analysis. The assessment or each area was undertaken separately and this concluded that the landfill material posed a risk to human health (lead, PAH’s and asbestos).
The preliminarily conceptual; model was refined and the assessment concluded that a cover system on and garden/landscaped area within the landfill was required.
The Phase II report was submitted (17/02163/F) with the memo from the contaminated land officer confirming the recommendations in the report had been accepted.
Prior to the commence of the construction phase the methodology of the remediation and details of the gas protection measures were required (remediation strategy / implementation plan), this confirmed the specification of the gas membrane as well as the other protection measures required. Once this was approved the pre commencement conditions were discharged and the construction phase could commence.
The development commence in September 2018 with the sit
e being visited a number of times to validate the gas protection measures and the installation of the gas resistant membrane as well as the placement of a 1,000mm cover on the landfill areas.
