Land Investigation – Phase One
Typically, the site investigation will be conducted in several phases. In the first phase of ground investigation, the site will be assessed to determine whether previous use may have caused contamination. This can be accomplished using previously gathered information from a desktop study.
At this stage, no physical investigation of the land will occur, and site investigations are purely preliminary. Background information can be gathered to find certain characteristics that must be considered before development or construction begins on the land. The desktop study may also reveal certain risks and allow them to be managed effectively by a local authority in London. This phase will produce a conceptual site model for the site and also help to determine the scale and detail of further investigations. As such, through an effective desktop study, it is possible to avoid expensive land or soil investigations if they are not necessary.
A walk over study will also occur in this phase to ensure that the information gathered through the desktop study is indeed correct. The site will be covered by an expert on foot, and a variety of information will be recorded, including issues with instability, vegetation and soil or rock or industrial contamination or activities which may not be picked up by the information collated during the desktop study.
Land Investigation – Phase Two
During phase two, any issues that arose through the phase one site investigation will be looked at in more detail, often using a variety of equipment. For instance, soil investigation will include groundwater and soil samples being collected by an expert environmental professional
The methods used to complete the second phase of the ground investigation will depend on a number of key factors, including previously established contaminants, accessibility and the geology. Methods used on previous local authority contracts in London include cone penetration tests.
Cone penetration tests can be used to evaluate geotechnical properties of soils. It is one of the most popular methods for this type of process. One of the benefits is that it can assess whether layers of soil will behave under different environmental conditions and proposed foundation loads. As such, it could be an important test for a range of different types of development. Other methods may include, window sampling and trial pitting.
Window sampling is a useful method for areas where disturbance needs to be minimised or a development location where access is restricted. Trial pitting, on the other hand, can be used to get larger soil samples where an in-depth visual examination is needed. One of the main advantages of this method is how rapid a soil investigation can be completed. However, it does often involve a great level of disturbance. This shows how the methodology for the second phase of a site investigation can be customised for the specific requirements of the development in question.
Benefits of Site Investigation
There are numerous benefits for local authorities and, clients in general, to carry out a site investigation and due diligence. Once ground investigation has been completed, a report with a full conceptual model of the site will be developed, and potentially a quantitative or qualitative contaminated land risk assessment. This report will show what the contaminant could affect or indeed, who it could affect, depending on what the site is going to be used for and provide preliminary geotechnical information for foundation design.
Using companies that provide professional land investigation service, local authorities can gain a massive amount of knowledge before building in a location. During the negotiation process, they will be able to comment on various issues or contaminants such as flooding and certain ground conditions. For instance, a ground investigation may show the risk of potential structural damage to any building developed on that site.
Completing this due diligence work can provide local authorities with important facts and details to consider during the process of completing the purchase of the site. A ground investigation is particularly recommended for those looking into the redevelopment of a brownfield site, or a site divestment. If you are completing a redevelopment on a previous brownfield site, using a team that is a member of the Society of Brownfield Risk Assessors (SOBRA), will ensure that you have the expertise you need on hand.