WM3 and Hazard Classification of Hydrocarbon Impacted Soil and Road Arisings

WM3 2015 published by the Environment Agency gives updated guidance on how to apply the correct hazard classification for soil contaminated by oily wastes. The guidance effectively divides wastes into two categories: wastes containing a known hydrocarbon type and wastes containing an unknown hydrocarbon type. Waste containing a positively identified hydrocarbon type can be classified on its type and total concentration, but wastes containing an unknown hydrocarbon type may be classified on either the total hydrocarbon concentration, or if between 1,000 and 25,000 mg/kg, classified using the marker benzo-a-pyrene.

The summary hazard classification is as follows:

If the concentration of TPH is  10% (100,000 mg/kg) the waste will be HP5* Harmful.

If the concentration of TPH is  3% (30,000 mg/kg) the waste will be HP10 toxic for reproduction.

If the concentration of TPH is  2.5% (25,000 mg/kg) the waste will be HP14* Ecotoxic.

If the concentration of TPH is  0.1% (1,000 mg/kg) the waste will be HP7 Carcinogenic and HP11 Mutagenic, if the concentration of benzo-a-pyrene is >=0.01% of the concentration of the TPH

If there is any uncertainty about the hydrocarbon type, the worst case scenario has to be adopted, requiring additional analysis for polyaromatics and BTEX. The guidance also states that any treatment of the waste such as bio-remediation, soil washing or thermal treatments, automatically re-classifies the waste as an unknown oil and will therefore also require additional analysis.The standard analytical method used for TPH in the laboratory is not always able to identify hydrocarbon types and cannot easily differentiate between weathered fuels and creosote or coal tar and ashphalt.

Most soils containing an unknown hydrocarbon can be classified as non-hazardous for HP7 and HP11 if the Benzo-a-Pyrene (BaP)BaP is <0.01% of the TPH value (<250 ppm for a TPH value of 25,000 ppm)

Soils containing Petrol above 1000 mg/kg or diesel above 10,000 mg/kg are automatically classified as hazardous and the use of BaP or any other marker is not allowed.

Analytical Uncertainty

Accurate analysis and hydrocarbon identification is therefore essential for correct hazard classification. The standard GC method can however incorrectly report that soils rich in natural organics, that contain no petroleum hydrocarbons, contain >0.5% TPH unless special procedures are used during the analysis. Accidentally including Road Tar in the sample will usually cause the lab to report a very high TPH, possibly as high as 2.5%. Bio-fuels also cause the standard lab method to report a very high TPH. The cost of treating or disposing of soils contaminated with fuel, oil, tar or creosote is high, with material classified as hazardous costing several thousand pounds per single lorry load to deal with. It therefore pays to be certain that the analysis used to classify the soil is the best available and only reports genuine petroleum derived hydrocarbons as petroleum hydrocarbons and is able to identify and differentiate between bitumens, creosotes and coal tars.

The sampling and testing methodology described in Appendix D of the new guidance clearly states that a statistically representative amount of sampling is required to effectively classify the waste. Contaminated soil is a heterogeneous matrix and will therefore require analysis of much more than a few samples per site to comply.

Landfill operators and soil treatment centres currently rely on the waste producer to correctly classify the waste, but retain the liability once waste is delivered. Any checks carried out on material arriving at the landfill or treatment centre currently takes several days or weeks before laboratory results are obtained to confirm the nature of the material. During this time, the entire shipment of material should be segregated just in case it has to be removed from site or an alternative treatment strategy proposed.

QROS provides an alternative approach that significantly improves analytical uncertainty and reduces the total soil disposal and/or treatment costs. QED analysis takes just a few minutes so loads can be checked as soon as they come onto site, minimising waiting time and reducing the chance of incorrectly classified material being incorporated into the landfill or treatment area. Combined with XRF, real time analysis of metals and hydrocarbons is now possible – and economically viable.

The QED has a small footprint, requires no gases, chlorinated solvents or special facilities for use and has very low running costs. Soil and water analysis takes less than 5 minutes per sample to provide BTEX, GRO, DRO, TPH, PAH and BaP concentrations, coal tar/ bitumen can be done in seconds. An on board fingerprints library for fuels, oils, tars and creosotes, derived from reference standards, is used to match the sample fingerprint, providing simple and reproducible identification. It is easy to use and can be operated after a few hours training for soil analysis, minutes for coal tar testing.

The fingerprint and low cost also makes the QED ideal for managing bioremediation, providing real time data that can be used to reduce the total time the soil is left in treatment.
The October 2020 Land Contamination Risk Management (LCRM) Guidance states that the Environment Agency will accept data generated by on site methods as part of the regulatory process provided the on site method has suitable QC and that a few confirmatory samples are analysed by an MCERTS accredited laboratory.

The EA recommends the use of on site analysis to improve the quality of the overall data package provided and to reduce costs.

The QED has been approved in the USA as a replacement for the laboratory Method 8015 GC-FID method for hydrocarbon analysis, so can be used with confidence that credible results will be generated.