Brownfield Assessments

Brownfield sites can have a wide range of sub-surface features associated with the former land use that can significantly affect the redevelopment of the site.

Features such as old foundations, piles or pile caps, voids, underground utilities and culverts, buried fuel and storage tanks, mine workings, archaeological features, buried reinforced concrete and unexploded ordnance can be present and can cause significant problems if not identified before intrusive work begins. Phase I Assessments can help identify if such features might be present but a geophysical survey can accurately locate them.

Phase Site Investigations Ltd have the expertise to tailor a geophysical survey to meet the individual project requirements and on larger sites can undertake trial surveys to assess which techniques will provide the required results.

Buried utility location

The accurate location of existing buried utility apparatus is key in any development involving excavation work. Not only is there a major health and safety issue with identifying the accurate position of apparatus prior to excavation but there can be significant cost and time implications if apparatus is damaged during exaction work.

Phase Site Investigations Ltd offer a range of services for locating buried utilities including compiling plans from Statutory Undertakers, a range of non-intrusive survey options, topographic surveys and drainage surveys.

Sub-surface hazard location

Sub-surface hazards can come in a variety of guises. Many occur on brownfield sites but others can be located under roads or car parks and on sites that may appear to be greenfield. If it is not identified or accurately located prior to excavation then the discovery of a sub-surface hazard can have a major impact on a development.

Hazards that can be identified using non-intrusive techniques include fuel and storage tanks, utility apparatus, pipelines, sewers and culverts, buried foundations, unexploded ordnance, voids, areas of contamination, piles or pile caps, mine workings and shafts, geological faults or variations, archaeological features, buried reinforced concrete or other structures, infilled quarries and landfills and contaminant plumes.

The possible presence of sub-surface hazards can be identified by a Phase I Assessment which, if the site conditions are appropriate, should then be followed up by a geophysical survey prior to intrusive work.

Geological mapping / ground engineering

There are a variety of geophysical techniques that can be used to obtain geological information and hence reduce or negate the need for intrusive work. Geophysics can be used to determine depth to bedrock, thickness of overburden, relative thickness of geological layers and information on the stratigraphy and lithology of the ground. Features such as clay packets, the extent of sand and gravel lenses, buried channels, cavities, dykes, faults and fractured zones can all be identified and there are techniques available that can aid in groundwater exploration and groundwater quality assessment. Geophysical methods can also be used to help determine engineering parameters such as density, soil stiffness and rock rippability.

Phase Site Investigations Ltd can obtain information on the general geological conditions of a site as part of the desk study component of a Phase I Assessment. Drawing on our combined engineering geology and geophysics expertise we can assess which geophysical survey techniques can provide the ground engineering or geological information that you require.

Roads

Ensuring that the road network is kept in good order is critical. Geophysics can be of huge benefit in road maintenance or assessment programs as data can be collected over large areas with significantly less disruption that intrusive work would entail.

One of the main uses of geophysics in highways assessments is to obtain information on the depth and condition of the layers within the pavement structure. This type of survey can often be carried out from a vehicle at normal traffic speeds. Geophysics can also be used to locate a wide variety of other features that underlie roads including voids, culverts, mine workings and utility apparatus. These applications usually require that the data is collected at individual stations or on a detailed survey grid and so traffic management may be required to ensure that health and safety requirements are met. Phase Site Investigations Ltd can carry out the geophysical surveys and also have operatives qualified to implement the traffic management.

Bridges

All bridges will require their condition to be assessed at some point during their lifetime, whether as part of routine inspections or in response to a defect. The assessment may involve the bridge structure and construction or the infrastructure that it carries, whether that is rail or road.

Geophysical surveys can be used to help determine bridge construction detail including identification of internal metalwork, material thickness and layers, reinforcement structure and detection of voids. Geophysics can be sued to assess the infrastructure, such as pavement construction information or ballast condition, with significantly less disruption that intrusive work would entail.

Phase Site Investigations Ltd have experience of a wide-range of geophysical and non-intrusive surveys that can be utilised to assess bridge condition.

Archaeological surveys

A planning constraint can be put on any development until the impact on any potential archaeology has been determined. To ensure cost-effective mitigation it is crucial that information on the presence and extent of archaeological remains is known as early in the design and development process as is possible.

Geophysics provides a reliable, well-established means of identifying archaeological remains and sites in both rural and urban contexts. The results of a geophysical survey can be used to target intrusive work or, if carried out early enough in the design process, can indicate areas which are free of archaeological remains and hence where development can be carried out with minimal impact on the archaeology. In both cases overall project costs can be significantly reduced. Geophysics can also be used to study historical buildings and structures, primarily to assess the condition of above ground remains or to locate underground features such as tunnels, culverts and cellars.

Phase Site Investigations Ltd can undertake archaeological desk studies, either as a stand-alone report or alongside a Phase I Assessment. We have expertise in a range of geophysical techniques and can assist in the procurement of archaeological excavations or watching briefs by working closely with specialist contractors.

Mineshaft and mine working detection

Records of coal extraction by opencast and deep mining methods have been maintained by the Coal Authority since 1872 but prior to that very few mining records exist. Even when records are available they are often incomplete or inaccurate and records for other types of mining or quarrying are generally even less comprehensive.

Phase Site Investigations Ltd can identify if there are any records of mine working or quarrying activity within a site as part of the desk study component of a Phase I Assessment. If a possible risk is identified then we are experienced in a range of geophysical techniques that can be used detect and characterise the features.

A geophysical survey can be undertaken to help locate and define the extent of the mining features, drastically reducing the amount of intrusive work that will be required to characterise the features. Depending on the size of the target feature a geophysical survey can be used to locate mine workings at depths in excess of 20m.

Unexploded ordnance detection (UXO)

The threat from unexploded ordnance is very real on certain sites. The risk of surface or near-surface small-arms UXO usually only occurs on existing or former military sites or sites where munitions were manufactured or tested although the presence of unexploded bombs can occur in any location that was bombed during WWII. Geophysics can be used to find ferrous and non-ferrous small-arms ordnance and deeper unexploded air launched bombs.

Phase Site Investigations Ltd can carry out the geophysical survey and analysis or by working closely with a specialist explosives ordnance clearance company can provide UXO risk reports, a site survey, including clearance, and the production of a clearance certificate. The location of air launched bombs generally requires the insertion into the ground of a ‘bomb probe’. Phase Site Investigations Ltd do not carry out this service in-house but by working closely with specialist operators we can sub-contract this service if required.

Buildings and structures

All buildings and structures require their condition to be assessed during their lifetime, whether as part of routine inspections, in response to a defect or a change in use. There is an increasing demand to utilise non-destructive techniques to achieve this, particularly where information is required over a large area or the structure is too sensitive to allow destructive investigation.

Phase Site Investigations Ltd can utilise geophysical and non-destructive techniques to help determine construction detail including identification of internal metalwork, material thickness and layers, reinforcement structure and detection of voids.

Rail

Ensuring that the rail network is kept in good order is critical. Geophysics can be of huge benefit in rail maintenance or assessment programs as data can be collected over large areas with significantly less disruption that intrusive work would entail.

Phase Site Investigations Ltd can utilise geophysics to provide information on the depth and condition of ballast material, the depth of material underlying ballast and depth to natural ground. It can also be used to locate a wide variety of other features that might lie adjacent to or underlie the railway including culverts, mine workings, animal burrows, pipes and cables or voids. Associated structures such as bridges and platforms can also benefit from geophysical surveys as part of maintenance programmes or to identify specific structural problems.

Landfill Assessment

Historical records are often incomplete for most closed landfill sites, and even some active ones, which can make the management and maintenance of such sites difficult as any intrusive work risks providing contaminant pathways.

Phase Site Investigations Ltd can use geophysics to determine the lateral and depth extents of the landfill boundaries or individual zones within the landfill, characterise variations in waste composition, including the identification of ‘wet’ and ‘dry’ areas, assess and monitor leachate plumes as well as identifying geomembrane leakage.