Out in the field
EBM looks at the increasing popularity of field-testing as a strategy for determining contamination levels at brownfield sites and discovers that it can offer cost benefitsOn-site characterisation of contaminated land is a rapidly growing area with huge potential. Traditionally, samples taken from a site are sent off to a laboratory for analysis but often this takes time and therefore adds costs to the development. Over the past few years field analysis techniques have developed enormously, and many experts feel that the time has come to employ them more often.
Paul Beck, chief executive of CL:AIRE, an organisation that carries out field-testing of contaminated land remediation techniques, is one such supporter of the emerging technologies. "The whole contaminated land management process in the UK has become risk-based," he says.
"Environmental risk is now about trying to relate a complex suite of contaminants to their impacts on a whole range of flora and fauna. We simply don’t have enough time in the next 100 years to try and figure that out."
Beck believes that this is where on-site characterisation tools come into their own. Because there is a much shorter time period to get results - no two-week wait for a laboratory to carry out the analysis - the potential exists to take more samples, giving a wider overall picture of contamination patterns.
"It’s all about making things cost-effective, being more accurate, and trying to get a better definition of the distribution of contaminants and knowing what the risks are going to be," he says.
And he is quick to point out that on-site testing cuts out problems associated with laboratory analysis, such as sample degradation due to losses of volatile components, or lost and damaged samples.
"Half the problem is taking a representative sample. Where is the sample from? Is the sampling regime adequate?" he says. "To do the sampling properly is expensive. So with these in situ techniques, you can get lots of samples for the same amount of money and they give you a very accurate picture of what is happening on the site."
This is a promising proposition for those used to traditional methods of site investigations where, as Bob Barnes from the Environment Agency's National Groundwater and Contaminated Land Centre, says: "You go onto a site where you think there is contamination, take samples and send them off to the laboratory. A fortnight later the laboratory says that you have got contaminants in this or that area and you then have to get all your gear and people back on site to determine exactly where."
Clearly, if that information is available while the investigation team is onsite, the opportunity exists to delineate the exact areas of contamination immediately, which creates cost and time savings. Effectively, the team can get more data and better coverage of data for less money.
Problems of accuracy
As might be expected there is a downside - that of reduced accuracy and sensitivity. The technology is definitely improving - five or six years ago, all that could really be hoped for from onsite characterisation was a result confirming the presence or absence of a particular broad suite of contaminants. Now it is possible to distinguish between say hydrocarbons and chlorinated hydrocarbons. The detectable concentration has also improved - from perhaps 1000ppm to within 10-20ppm.
However, Douglas Stevenson, a partner in environmental consultancy ERM’s site investigation and remediation team points out that even that kind of accuracy is inadequate for risk assessments.
He says: "We do use field characterisation tools, but we use them very much as a first pass or indicator in the field if we are looking to do a job in a hurry. We would always back that up with laboratory data."
"Field characterisation has its uses - and can be a very powerful tool - but there are inherent risks in terms of reliability and accuracy. We would certainly be very uncomfortable with solely using those techniques."
The bottom line is that - despite the sector’s rapid developments - laboratory testing still offers the precision required when planning remediation projects.
Added to doubts about the accuracy of the techniques is the relative lack of information about field-testing. In a remediation market where accuracy is extremely important, many innovative technologies remain unproven - sufficient data on their effectiveness simply doesn’t exist.
The Environment Agency has set out to rectify this situation, by starting a project to review the application of field techniques. Research is being carried out by the National Groundwater and Contaminated Land Centre, and results are expected to be available by mid-summer.
The project aims to: identify a range of current and future technologies and techniques that can characterise contamination levels or be used as monitoring tools during remediation and long-term monitoring programmes; to detail how relevant they are to different contaminants and media; and to define suitable roles for different techniques in remediation programmes.
"We will publish the results so that people can use the report as a reference material and we are looking to develop Agency policies related to the use of these techniques," says Barnes. "We may also look at developing standard operating procedures so that there is a degree of quality assurance."
Although a significant amount of research has been carried out by the US Environment Protection Agency’s Technology Innovation Office, Barnes says it is important to show the technique being used is valid for each site. "You have to look at the UK’s geology and regulatory regime," he says.
Striking a balance
The field characterisation techniques in question offer an alternative to traditional laboratory analysis of soil and water samples. They are effectively tools and techniques - chemical, biological or physical - that can be used in the field, either in situ or in field laboratories, to provide real-time analysis and testing.
Realistically though, on-site testing is complementary to laboratory analysis, rather than a potential replacement. "In general, field techniques give you less accuracy, so it’s a case of designing an investigation carefully and understanding what quality of data you are going to get," Barnes says.
"You need to ask if a certain tool is going to give you a high enough level of accuracy, or whether you will still need to take some samples and send them off to a laboratory so that you have an sufficiently accurate indication of contamination levels. It’s all down to what you want to do with the data""
These are exactly the questions the investigation is out to answer. What are the tools’ limitations and where can they offer real gains in the way contaminated land is treated in the UK?
"We need to ensure that there are enough case studies to show that the techniques are going to work. People need to have confidence in the data that’s produced so it can be used as part of a regulatory decision, or legally during due diligence." says Barnes."
If the study is as comprehensive as the Agency promises, field-testing, as well as seeming like a good idea may actually become a proven practical option. Used in conjunction with laboratory testing, it has the potential to save time and money - music to most developers’ ears.