phase 1 assessments

The first stage of any site investigation is to undertake a Phase I assessment, also known as a desk study report. Phase I assessments, and subsequent investigations, are essential as they provide information that is critical to making an informed decision on the viability of a development.

A Phase I assessment is primarily used to indicate if there are any factors that may cause problems in the development of site. The investigation will highlight potential risks to the proposed development, will indicate if further investigation is required and suggest what remediation or design solutions may be needed.

If the assessment highlights hazards, such as buried features, then further work will be needed to define their exact location and extent. The traditional method for doing this is to carry out a Phase II assessment (an intrusive investigation using trial pits and boreholes) but this has limitations in that only a relatively small amount of the site is sampled. If the site conditions are suitable, then a geophysical survey can be the most cost-effective method of identifying hazards as it can be used over all accessible parts of the site. Geophysics can be used to locate a wide variety of buried features, including old foundations, mineshafts, mine workings, utility apparatus, oil drums, fuel tanks, archaeological features, in-filled basements, tunnels, voids, landfill extents and contamination plumes.

A Phase I assessment involves collating and interpreting information from various sources in relation to the proposed development at a site. In the first instance the following sources and / or methodologies will be used:

• Site visit and walk over survey
• Historical Ordnance Survey maps
• Geological maps (largest available scale and most recent maps)
• Geological memoir
• Groundwater vulnerability map
• Environmental issues such as nearby landfill sites, waste management facilities, etc
• Past mining activity
• Existing borehole records, if available from the British Geological Survey or Local Authority archives
• Previous geotechnical reports, if they exist
• Local knowledge of the site, if available
• Aerial photographs
• Old building plans (if the site was previous developed)

Phase Site Investigations Ltd can undertake Phase 1 assessments utilising our experience of engineering geology and geotechnical engineering. Recommendations will be made on the amount and type of further investigation that will best benefit your project.