The Government has said that over the next five years it plans to directly commission the construction of thousands of new homes on public land. David Cameron described this announcement as the biggest shift in house building policy in the last 30 years.
These plans will be backed up by an extra £1.2 billion to help remediate brownfield sites for tens of thousands of new homes across the country. This is an important step forward, with the Campaign to Protect Rural England (CPRE) estimating there is capacity for at least one million new homes on suitable brownfield land in England alone.
For anyone seeking to build in these areas, however, there are a number of environmental considerations to take into account. The ground in UK brownfield sites is highly likely to contain a wide range of contaminants, and accurately determining the levels of these hazards within the soil must be a priority for developers across the country.
So, what are some of the various toxins buried beneath the UK’s surface, and how are the latest cutting-edge detection technologies being used to identify them?
POP problems and new waste guidance
In 2015, the Environment Agency updated its technical guidance on the assessment of hazardous waste, through a consultation document known as WM3. As part of WM3, soils on brownfield sites that could potentially contain dangerous substances must be tested to determine if harmful levels of pollutants are present.
There are countless potential hazards that can be hidden within soils, but the WM3 guidelines put a strong focus on monitoring for high levels of Persistent Organic Pollutants, more commonly known as POPs. This family of toxic chemicals can cause a wide variety of ecological, health and safety issues for land developers. Coming into contact with even trace amounts of some POPs can result in developmental defects, chronic illnesses, and in extreme circumstances, even death, which means identifying any potential sources must be a priority when building on brownfield sites.
In the UK, POPs have previously been used to manufacture pesticides and industrial chemicals. In some cases, these have inadvertently leached into the surrounding environment following agricultural processes or industrial activity. Although they have been banned in many countries, POPs can still be found in waste and soils around the world.
POPs can make their way into the soil via a number of routes, including through contaminated groundwater or precipitation. Once in contact with the ground, POPs can bind themselves to soil particles and deteriorate extremely slowly. As a result, they can accumulate into dangerous quantities, posing a significant risk to those exposed to them.
The manufacture, sale and use of products containing POPs is banned in the UK, but identifying dangerous levels of them within ex-industrial sites is still a key issue that developers must address.
Dioxins, furans and dioxin-like PCBs
There are dozens of different pollutants that are classed as POPs. Some of the most dangerous are dioxins and furans. If a soil sample is found to contain these compounds, a concentration of only 15 µg/kg will render it hazardous under WM3.
Dioxins and furans are usually produced as a by-product of industrial processes and can be found in a variety of places, especially on sites where waste from manufacturing or chemical processes has been stored. Studies have suggested that they can also be found in emissions from the incineration of hospital or municipal waste, car exhausts, and even in the burnt residue of some solid fuels.
Research indicates that coming into contact with dioxins and furans can result in cancer, birth defects and respiratory issues, as well as brain and kidney damage. Humans are most commonly exposed through ingesting the pollutants after they make their way into the food chain.
For this reason, one of the greatest concerns for environmentalists is monitoring dioxin and furan levels within soils and sediments. In most countries, as standard, dioxin levels should not go beyond 1,000 parts per trillion (ppt) in soils and 100 ppt in sediments. If this trigger limit is exceeded, the ground will need to be remediated as soon as possible.
Polychlorinated biphenyls (PCBs) are another highly toxic type of POP which are also banned in the UK, but still may be present in dangerous levels within the country’s brownfield sites. In the past, PCBs have been used as dielectric filler liquids in some types of electrical equipment. According to the Health and Safety Executive, these include transformers, switchgear, capacitors and the starter units of fluorescent lights and fractional horsepower motors.
Like dioxins and furans, exposure to PCBs poses a major risk to humans, animals and the environment. PCBs can build up inside the body, entering through direct contact, inhalation or ingestion. A notable case of human exposure to PCBs can be found in the American town of Anniston, Alabama, where a chemical manufacturing company dumped millions of tonnes of PCBs into the area’s landfill and creek. This resulted in the poisoning of the town’s water supply and a $700m lawsuit.
One of the most effective methods used by laboratories to test for dioxins, furans and PCBs is High Resolution Mass Spectrometry (HRMS). This technique allows for a compound’s molecular weight and elemental composition to be identified and measured to an ultra-precise degree. When compared to Gas Chromatography Mass Spectrometry (GC/MS), HRMS is a significantly more accurate determiner of a compound’s make-up. In advanced laboratories, this method can be used for the analysis of a wide range of organic contaminants.
PAHs and TPHs
Smoke from the incomplete combustion of carbon-based materials, such as coal, oil, gas and wood can result in the build-up of other contaminants, known as Polycyclic Aromatic Hydrocarbons (PAHs) in soils. There are several hundred types of PAHs, but the most common is Benzo[a]pyrene (BaP). The presence of BaP is commonly used as an indicator species for PAH contamination and has been proven to be a carcinogenic compound.
As part of the recent WM3 update, BaP is used as a marker compound to test if waste material is carcinogenic or mutagenic. In soil containing unknown oils, for example, the concentration of BaP must be less than 0.01 per cent of the concentration of TPHs (Total Petroleum Hydrocarbons), otherwise it is classed as a hazard.
The presence of waste oils, such as fuel oil, diesel and biodiesel in soils is of particular concern for land owners, as they are usually an indicator of a leaking underground storage tank. Once contaminated with high levels of TPHs, the earth must be classified as hazardous waste under WM3, and must be disposed of accordingly. This is made much easier when the oil in the sample can be accurately identified.
Oils in waste can be identified via a number of methods, including GC-FID (Gas Chromatography- Flame Ionisation Detector), in which TPHs are extracted with solvents. GC–FID tests use carbon as an identifying compound, which means organic impurities in a sample, such as leaves, may impact results. To address this, silica and sodium sulphate are used to extract non-fuel contaminants. In our experience, we’ve found that clients are more interested in silica clean-up and are now asking for it as standard.
Identifying diesel can be a challenge, as its chemical pattern will change during the sampling process. However, an experienced chemist will be able to accurately determine its presence in a soil. When there are mixed fuels present, advanced chemical fingerprinting techniques or fuel forensics methods can provide more detailed results.
Asbestos: another hidden threat
POPs aren’t the only hazard in soils that developers must pay close attention to. The UK’s Construction Industry Research and Information Association (CIRIA) claims that there is still a large amount of undiscovered asbestos hidden within Britain’s brownfield sites.
Currently anything under 0.001 per cent asbestos in soil fibre is widely thought of to be a safe level, although the Construction Industry Research Information Association (CIRIA) has suggested to the industry that this is not necessarily suitable in all cases as it fails to take into account a variety of factors, such as the range of soil types in the UK and their differing compositions. For example, dry, loosely-packed sandy soils could release more asbestos fibres when disturbed than wet clays. This is an issue that, if not taken into account during the testing and remediation stages of a development project, could lead to unsafe airborne asbestos levels on site.
Although the Control of Asbestos Regulations 2012 (CAR) requires UK landowners and developers to take steps to protect workers and the general public from asbestos exposure, no legislative guidance so far has been given regarding what constitutes a dangerous level of asbestos in soil.
Minimising metal risks
Alongside asbestos and POPs, heavy metals, such as mercury, lead, zinc and arsenic can also become an issue for land developers, especially in areas like many of Britain’s brownfield sites where manufacturing or chemical production operations have previously been carried out. These are, of course, naturally present in small quantities in soil, but industrial activities can lead to an increase in concentration that can prove harmful to animals, humans and the environment.
Arsenic, one of the most common causes of metal poisoning, is sometimes released into the environment by the smelting process of other metals, such as copper or zinc. In the UK, there are a variety of instrumental techniques for the determination of these compounds. Inductively Coupled Plasma – Mass Spectroscopy (ICPMS) analysis enables laboratories to offer extremely low detection limits for a variety of samples types, with the quality, robustness and speed that customers require.
Testing for contaminants
Testing different soils can throw up a range of challenges for laboratories and handlers to confront. In 2016, UKAS’s Deviating Sample Policy has had a significant impact on sampling, analysis and data validity in the UK. The policy requires soils to be tested within particular timeframes, as some contaminants can deteriorate quicker than others. PAHs, for example, must be tested within 14 days otherwise the sample will be declared as deviant by regulators. With this in mind, one of the growing requirements for testing soil is faster laboratory processing, with the most efficient labs now offering five day turnaround times as standard.
The way samples are stored and transported is also an important factor in the UKAS policy. In 2016, regulators are increasingly questioning the validity of reports and developers must ensure they are kept up-to-speed with the correct handling procedures. For PAHs, for example, these must not come in clear glass jars, as the compounds are photo-sensitive and can degrade if exposed to light. It is important that robust extractions take place alongside state-of-the-art analytical techniques, if they are to produce accurate and reliable results.
The most sought after environmental chemistry laboratories will offer a comprehensive range of UKAS and MCERTs accredited tests for contaminants in soils, continually enhancing their offerings to keep up to date with and meet the requirements of the Contaminated Land Assessment Guidance.
Moving forward in 2016
Over the last decade, the field of analytical chemistry has developed to face a number of challenges in the environmental industry. The industry has advanced from the use of traditional, slow and trouble-some methods to fast, sophisticated techniques that are used to analyse for hazardous compounds in complex matrices. This evolution of environmental chemistry continues with advances in hyphenated techniques, software development, instrument sensitivity, selectivity, compound confirmation and lean production practices.
With so much to gain over the coming years from the development of Britain’s brownfield sites, making sure that the ground is safe to be built on must be one of the first steps towards solving the housing crisis. It is up to the developers of these sites to take advantage of this continually advancing sector and keep themselves up-to-date with the latest soil testing techniques so they can reduce the threat of regulatory challenges to their projects.
Published: 11th May 2016 in AWE International