The site reconnaissance and walkover survey forms part of the desk study. A desk study and a reconnaissance survey (also known as a phase 1 desk study) should be carried out as part of the site investigation and preferably prior to development though this is not always possible. The purpose of the desk study is to provide an initial overview of the nature and extent of any geotechnical, environmental or contamination hazards that may exist.
Depending upon the requirements of the proposed development the desk study can be focused on different aspects including; geological, flood risk, environmental, geotechnical, planning application and pre-purchase assessments.
The search should include a review of historical maps, aerial photographs, register searches, and consideration of the geological, hydrogeological and hydrological conditions. The report will identify potential hazards such as ground instability, mining activity, landfill, potential sources of historical and contemporary contamination and pollution incidents
A walkover survey of the site and surrounding area allows any obvious visible or noticeable surface issues to be identified, including polluted surface water and nearby sources of potential contamination. The desk study enables conclusions to be drawn regarding the pollution and contamination risks. Where appropriate the walkover survey may also include knocking on doors and obtaining as much first-hand knowledge on the sites history.
The research is used in the compilation of an outline conceptual ground hazard model (CSM) and a preliminary qualitative risk assessment. The model helps us to understand the environmental impact on the proposed development and, if deemed necessary, is critical in the design of an appropriate intrusive investigation.
Under current legislation desk studies are required as part of the planning process. The presence of contamination is a key concern of the regulatory bodies when considering proposals. The developers have an obligation to comply with the environmental regulations at each step of the planning, design and construction process. The local planning authorities also have a duty to identify, investigate and require remediation of sites if pollution or contamination is considered to be likely or has been proven. A desk study and the walkover and reconnaissance survey are important elements in the initial stages of this process.