Location, location, location . . .

Essentially, GIS combines layers of spatial information about a location. It allows the user to visualise, manipulate and analyse data from many sources – databases, CAD plans, photographs and spreadsheets. Until recently, GIS required extensive dedicated resources and was not readily available as a desktop application. However, with recent progress in hardware and software, GIS has become much more accessible and now has a very wide application base.

In order to understand the environmental risk at a site, it is important to develop a conceptual model of the site that describes the site’s hydrogeology and identifies sources where chemicals of concern (CoCs) exist in the soil and groundwater; local receptors, which could potentially be impacted by the CoCs; and transport and exposure pathways, by which the sources and receptors could be linked. The nature and extent of CoCs, the positions of human and ecological receptors, and the nature of the geology and hydrogeology of the subsurface are key elements in the evaluation of environmental risk. These elements are readily integrated and communicated using a suitably designed GIS. The representation of such a conceptual model with a GIS facilitates the risk management and communication process, the selection of any necessary remedial action and, where appropriate, the selection of the most suitable end use.

Frequently, much information is available pertinent to the condition of a site, such as historical land use and results from intrusive site investigations. However, in many cases this information is scattered throughout numerous hard copy reports and is effectively wasted. A properly designed GIS can retrieve this information and maximise its value.

The use of a GIS system provides a number of significant advantages:

• Reduced cost – it allows cost-effective management of large environmental and facility data sets. It streamlines reporting and reduces the cost of compliance monitoring regimes.
• Risk & Liability Management – it allows complex analysis and risk assessment to be easily communicated, enabling asset managers in understanding and agreeing to remedial strategy.
• Data Ownership – user-friendly and desktop PC-driven system allows companies to be owners/managers of their own data without over-dependence on consultants.

The Shell GIS Toolkit is a suite of commercially available applications which have been integrated by scientists at Shell’s Westhollow Technology Centre and Cheshire Innovation Park. The main uses of the GIS Toolkit are:

• to store past, present and future pertinent soil and groundwater data in a suitable form,
• to be able to use the data in routine reporting,
• to be able to use the data as input to groundwater models, and
• to be able to visualise the data and the outputs of risk assessments.

The toolkit consists of threemajor components – a GIS, a database management system and a modelling package. At the heart is the EQuIS database system, an MSAccess-based application for the storage and retrieval of geological and chemical data from site investigations and groundwater monitoring. Details such as borehole/well location, stratigraphy, water level and chemical analytical data can be imported. The database has an open architecture and can interface easily with a range of applications – GIS, groundwater and solid modelling, borehole logging etc.

Data import

An important feature of the EQuIS application is its ability to import chemical analytical data from the laboratory in electronic form. This is done by supplying predefined EDD (Electronic Data Delivery) templates to the laboratory. This completely eliminates any corruption of the data which can occur during transcription from hard copy reports. A module is also available to allow the laboratory to check the integrity of the file before delivery to the client, so that error-free import of the new data into the database by the client is assured.

Once the data is in the database it can be used by other applications. Thus with the geological data, borehole logs may be produced by a borehole plotting package (e.g. LogPlot), or the stratigraphy may be visualised at selected borehole locations using the GIS (ArcView), or else solid models or fence diagrams produced via a modelling package (e.g. GMS). The chemical data can be queried from ArcView on the basis of a variety of parameters such as sample media, groundwater zones and locations, and comparisons made of chemical concentrations against risk-based screening levels. Hydrogeological data can also be exported from EQuIS into a groundwater modelling package such as GMS, so that groundwater flow, particle tracking and fate and transport modelling can be accomplished. Results from the modelling studies can then be imported into the GIS as layers, to give an integrated picture of the site environmental risk.

Property management

A chemical works had been operated for more than 50 years. Over the years significant geotechnical and environmental investigations had been undertaken and the results reported in numerous reports. The GIS toolkit was used to collate all the information to allow the property manager to understand the environmental risks and liabilities associated with particular parcels of the site.

Shell Global Solutions also prepared a groundwater model for the site to assess if the benzene levels identified in the soil and groundwater represented a risk to human health and groundwater receptors. The groundwater model required a comprehensive understanding of the underlying geology.

Borehole data were exported directly from the database into the modelling software, which was used to construct a three-dimensional solid model. From the solid geology model a groundwater model was constructed to reproduce and represent groundwater flow. This was calibrated using site measurements. Virtual particles were then placed into the groundwater at the two major sources to investigate whether they would reach the two main receptors, a nearby river and canal. Predictive benzene plume modelling demonstrated that the plumes stabilise after approximately 15 years, and do not reach the two major offsite receptors. The model was run for a period of 50 years – the age of the plant – and used a very conservative decay rate.

Using this approach, the Shell Global Solutions team were able to demonstrate that, even after 50 years, contamination was contained within the site boundaries and would not reach the major offsite receptors due to natural attenuation.

Tank ranking

Facility asset managers need to maximise the efficiency of facility maintenance and inspection regimes by optimising resources to address the highest risks. In the case of storage tanks, for example, risk reduction may be gleaned by moving from routine to tank-specific maintenance programmes, based on an understanding of the risk to the environment of leakage from each tank. Shell Global Solutions has developed a GIS-based tool for deriving a tank risk ranking based on modelling the consequences of catastrophic tank failure.

First, tanks are located from a CAD plan. A tank inventory provides data on tank contents and capacity, which allows a determination of the ecological and human health hazard associated with the contents of each tank.

The GIS facilitates the incorporation of data on tank contents, hydrogeology and receptor proximity into a spreadsheet-based model, which provides an assessment of the likely environmental impact of the failure of each tank. The resulting risk ranking, visualised in the GIS, offers a valuable resource for the prioritisation of tank maintenance.

GIS – the view on the ground

Part IIA of the Environmental Protection Act 1990 puts new responsibilities on local authorities to deal with the issue of historically contaminated land. This has knock-on effects on private sector industry and landowners who may own or occupy such land. Indeed, the decision-making activity of local authorities may have balance sheet implications – land values fall when the Contaminated Land label is used. Last year, Michael Meacher wrote to the CEO’s of FTSE listed companies urging them to take action against the backdrop of this Act. An assessment of the contamination aspects of sites is also a key component of legislation affecting current site operations. Applications under IPPC, for example, require information on land quality at the outset and use this as a yardstick to show land quality has not declined over the period of the Permit to Operate.

Spatial context

The management of the contamination aspects of land requires the arrangement of data in a spatial context. Key within this is the need to identify a source of contamination (i.e. material in on or under the ground), a sensitive receptor (i.e. human beings, livestock, crops, ancient monuments etc) and a pathway which links the two. A relationship between the source, pathway and receptor forms a pollutant linkage and is a key aspect of the definition of land as contaminated. The need to consider these pollutant linkages requires consideration of a large amount of differing data in different formats. This will, for example, include map-based information (e.g. previous site use, current use, the proximity of land of ecological significance, sensitive groundwater etc.) as well as other data from disparate sources (e.g. site reports, monitoring results, photographs, letters, diagrams etc.). Whilst Geographic Information Systems (GIS) are key tools to help organise and visualise the map-based data, GroundView, a UK GIS-based tool to help deal with information regarding contaminated land, enables the management of all of this data in a single system.

GroundView has been installed and operated in local authority offices for more than three years. The system extends GIS functionality by linking a GIS to a database, which enables users to store all land quality information in one place, offering time-saving and efficiency benefits via an auditable information management system. GroundView also enables the generation of any number of predefined reports at the touch of a button. Overall, the use of GroundView makes the user better able to account for their decisions.

In addition, a Site Prioritisation Tool can be added as a further module. This produces a risk grid, which identifies high-risk sites that may be prioritised for further action. This enables the user to easily apply a consistent set of rules in a transparent way thereby easing and adding a robustness to the decision making process.

Database links

Recent developments to the system have resulted in links to other databases, such as those which manage other environmental information (e.g. waste arising, noise, air quality). Again the system benefits from having all the data together in an integrated system, but map-based information showing key data, which can be downloaded onto a web site, is an added feature. Data analysis, graphing and reporting tools can also be included.