The management of contaminant issues on large sites with multiple pollutant sources or complex geologies presents a challenge to site owners. Site investigation is an iterative process with staged investigations and data gathering sometimes taking place over multiple campaigns. Traditional approaches can be slow, costly and disruptive to on-going site operations.
Within a standard site investigation strategy a limited number of soil and groundwater samples will be collected, often no more than two or three samples per hole, with a large emphasis placed on observations made during the excavation of the borehole or trial pit. Laboratory results will commonly be available only weeks later. While this is often adequate for sites with simple geology or a straightforward contaminant distribution, for complex sites this approach may lead to an inconclusive or unreliable understanding of the sub-surface situation. These are often accompanied by a recommendation for further multiple phases of investigation, due to an absence of fine detail on the soil strata or contaminant distribution.
An alternative strategy is to adopt a High Resolution Site Characterisation approach, using equipment such as a Membrane Interface Probe (MIP). MIP drilling can provide near real-time results - allowing the investigation to be adapted in the field eliminating the need for return visits - and collects data on a much more detailed basis (on a “cm” scale) allowing contaminant distribution or soil strata to be precisely mapped. This typically provides higher levels of confidence in the data by all stakeholders, fewer phases of investigation and precisely targeted, and hence cheaper, remediation. The way that data collected over time is collated is also extremely important. A traditional approach involving multi-phased investigations and individually reported groundwater monitoring rounds results in the potential to have important pieces of data that become forgotten (or are not used in developing an overall understanding of the site and contaminants present) potentially wasting significant amounts of money and allowing poor decisions to be made. In the worst case inappropriate levels of risk can be determined as the whole dataset has not been fully assessed. This can lead to remedial effort being committed when it would not necessarily have needed to be undertaken.
By developing simple data management protocols, holding information in a database and integrating it with Geographic Information Systems and 3D modelling packages, powerful, quick and robust interrogation of the dataset can be undertaken for sub-sets such as, groups of monitoring locations situated within a source area and wells down gradient. Data can then be mapped, tabulated or graphically presented which enables both the client and user to get much more from it.
Once an appropriate dataset is collected then robust consideration of what the implications are is required through the site characterisation process. Risk assessment is a key element in determining what, if any, remediation is required both within the framework of providing a sustainable solution such as how much contaminant needs to be treated; and providing a predictive management tool that allows further consideration of what aspects of the site condition are important and how this affects prioritisation of issues.
Assessing how sustainable any remedial activity is likely to be is another aspect that can provide significant cost savings. Sustainable remediation is fully embedded in the UK regulatory framework, and provides an opportunity to consider the whole life cycle implications of undertaking the remediation and weigh these benefits against other costs such as carbon expenditure and impacts of the works on neighbours. When remediation is required a robust Options Appraisal, fully considering sustainability, should be a high priority.
High Resolution Site Characterisation, good data management, risk assessment and alignment of goals with sustainability criteria can all reduce remediation costs and improve the certainty of remediation performance. Site assessment may appear a costly activity but when carefully designed and implemented it can result in substantial cost savings.
Want to know more?
For further information please contact Paul Hesketh, Technical Director, Contaminated Site Management Practice