The Different Stages of Site Investigation

The Different Stages of Site Investigation A site investigation is undertaken to comply with Regulatory requirements (necessary) and to minimise exposure to risk (desirable). Traditionally there are six stages to a typical site investigation; • • • • • •

Desk Study, Site Reconnaissance, Site Exploration and Sampling, Field Test/In-situ Test, Laboratory Testing and Report Writing.

Here we explore each of these phases in more depth as well as new ways the process could potentially be broken down.

1. Desk Study or Phase I Geo-Environmental Assessment This is the preliminary stage of the site investigation and comprises the scrutiny of a wide variety of collective information sources relating to the site such as historical maps, drawings, local authority information, published geology, hydrogeology, hydrology, environmental, mining, and unexploded ordnance. Where available, statutory services information may also be included.

The information gathered is then used to construct a ground and conceptual site model (CSM) followed by an environmental and geotechnical risk assessment. The Desk Study provides the framework and scope for the next stages of site investigation where required.

2. Site Reconnaissance The initial phase (preliminary investigation) involves early examination of the site by specialists. Information is collected during a site walkover survey to acknowledge possible site restrictions relating to the; terrain, existing structures, utilities, environmental, seasonal and ecological constraints. The condition of land surrounding the subject site are also considered.

Local conditions noted at this stage will help generate an adequate exploration design and prepare for the future intrusive ground investigations. Photographs will be taken at this stage as a record of the site details during the initial walkover survey.

3. Site Exploration & Sampling Next a more detailed ground investigation is carried out to establish the general geological, hydrogeological and sub-surface soil conditions. Comprehensive

information relating to the underlying geology and groundwater conditions can be collected using geophysical surveys, trial pits, boreholes and dynamic probing.

Additionally, at this stage of the site investigation, samples of soil, rock and groundwater can be collected for further examination and laboratory analysis.

4. Field Test/In-situ Testing During site exploration, testing can be carried out either prior to or during the construction process. In-situ ground testing can include hand shear- vane, standard penetration tests, cone penetration tests, structural loading tests and displacement observations (California bearing ratio, plate load and pressuremeter testing).

5. Laboratory Testing Representative samples collected during the intrusive investigation can be sent to the laboratory for further geotechnical and chemical testing. Soils and be tested for chemical quality, permeability, shear strength, compressibility to confirm geotechnical parameters.

Tests can be carried out on soil and groundwater to check for potential soil reactions to construction materials and chemical analyses.

6. Report Writing The final stage of the site investigation collates all the findings of the five previous steps into a report. This report will include all the information required before designing and building the final structure, safe in the knowledge all eventualities have been considered.

The report will feature details of the historical land-uses, geological and hydrological studies, results of any geotechnical or chemical testing and potential Phase I GeoEnvironmental recommendations relating to further investigations and testing or to the design and construction of the proposed works.

Although the aforementioned six stages are common when undertaking a site investigation, the process can be defined in other ways. According to ‘Planning and stages of site investigation’ by Peter G. Fookes in the second volume of Engineering Geology; the process can also be defined as a three stage model (I) Site Exploration, (II) Site Investigation and (III) Foundation Investigation. Fookes states that any works carried out prior to construction can be placed into one of the first two stages and anything happening during or post construction can be considered at stage three.

Whichever way you choose to delineate site investigation, all stages can be involved at one time or another. Alan Wood and Partners specialise in all stages of site

investigations and act as experienced construction site supervisors in many diverse building projects from major multi million pound developments to minor structural repairs to buildings.

If you need a site investigated in the future, get in touch with the experts at Alan Wood. www.alanwood.co.uk Â