A Walkover Survey is a key part to the Phase 1 Desk Study and includes a visit to undertake a visual assessment of the site and its immediate surroundings. Photographs are usually taken and any potential ground problems or contamination sources identified during this reconnaissance which may not be evident from the historical map search. These can include, for example, above and below ground tanks, asbestos containing materials and any ground stability issues.
The Desk Study should be carried out as the preliminary stage of any investigation and is typically required to satisfy planning conditions. The aim is to formulate an initial conceptual site model (CSM), which highlights the potential sources of contamination, receptors and the pathways between them. This “conceptual model” is critical in designing an appropriate Phase 2 intrusive investigation. However, it should be recognised that both phases of investigation are commonly combined into a single contract in order to save time and reporting expenses for our clients.
Under current legislation the provision of a desk study is typically a minimum requirement when submitting a planning application. The presence of contamination is a concern for the regulatory bodies when considering development proposals. The developers have an obligation to comply with the environmental regulations at each step of the planning, design and construction process, and the local planning authorities have a duty to ensure any investigation and remedial work is carried out in accordance with current guidance to an acceptable level. An environmental risk assessment is a key element in the initial stages of this process. The Desk Study Report follows the recommendations in EA Contaminated Land Report 11 (CLR 11) and EA Guidance on Requirements for Land Contamination Reports.
A comprehensive report will commonly provide the following datasets:
Ordnance Survey, Town Plans and Aerial Photographs to allow us to assess existing and former land uses
Initial simple flood risk potential by reference to Environment Agency mapping and British Geological Survey records
Solid and drift geology by reference to British Geological Survey mapping and borehole index
Groundwater vulnerability from Environment Agency classification of aquifer status
Consultation with local authority Environmental Unit (if applicable)
Assessment of potential subsidence issues from examination of geological maps, boreholes index and Brine Subsidence search for sites within relevant areas
Active and historical surface and underground workings based upon published information and internal records
Coal Authority Mining Report if site is within Mining District
Active and closed landfill search within 500m of the site boundary based upon local authority and Environment Agency records Active and closed landfill search within 250m of the site boundary based upon local authority and Environment Agency records
Radon gas potential with reference to Heath Protection Agency records.
It should be noted that Limited Desk Studies are designed for geo-environmental purposes only and do not include Structural Surveys, Buried Services Surveys, above ground or building Asbestos Surveys, Unexploded Ordnance Surveys or Invasive Plant Surveys for Japanese Knotweed, Giant Hogweed, Planning History, Archaeological Assessments, Planning,vHistory, Ecological Assessments etc. Preliminary Archaeological Assessment based on reference to National Monument Records
