Hazard Classification of

Hydrocarbon Impacted Soil on

Contaminated Sites for Contractors

WM3 2015 has been published by the Environment Agency giving updated guidance on how to apply the correct hazard classification for soil contaminated by oily wastes. The guidance effectively divides wastes into: 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 folows:

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. 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.

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.

The waste producer is legally responsible for identifying the waste and applying the correct hazard classification.

Analytical Uncertainty

Accurate hydrocarbon identification and analysis is therefore essential for correct hazard classification. The standard GC method can however incorrectly identify coal tar, creosotes and bitumens as degraded diesel as well as report that soils rich in natural organics, that contain no petroleum hydrocarbons, contain >0.5% TPH unless special procedures are used during the analysis. The penalties incurred from an incorrect classification can be substantial as can the cost of unnecessarily disposing of soil as hazardous. 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 yet is able to identify bitumens, creosotes and coal tars as well.

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.

QROS provides an alternative approach that will significantly improve analytical certainty and reduce the total analytical and soil disposal/treatment costs.

The QED HC-1 on site hydrocarbon analyser identifies the hydrocarbon type as well as giving the concentration of total BTEX, GRO, DRO, total aromatics, sum 16 PAHs and BaP .

The sample fingerprint is matched to an on board fingerprint library of fuels, oils, creosote, bitumens and tars to confirm the hydrocarbon type. Mixed hydrocarbons can also be identified with the approximate proportion of each hydrocarbon type calculated. Detection limits are 0.1 mg/kg for most fuels and the BaP detection limit is 0.002 mg/kg, which is more than adequate for the 0.01% limit for BaP at the 1000 mg/kg TPH lower limit decribed in WM3.

The QED has a very low response to naturally occurring compounds and this significantly reduces the incorrect reporting of humic acids or biofuels as TPH.

The complete analysis takes just 5 minutes, including sample preparation.

The QED automatically matches the sample fingerprint (black) to library fingerprints to obtain a match. In the example to the left degraded diesel (red) is selected. The similar shape confirms the sample as containing degraded diesel. The purple line is residual hydrocarbon which is also matched to the library. The results also show a confidence value for the match.

Can the QED be used in the UK ?

The June 2015 MCERTS Policy update states that data from on site methods will be accepted for regulatory purposes provided the on site method has suitable QC procedures and that the data is confirmed by sending a few samples for MCERTS accredited laboratory analysis.

In the USA, the QED is now mandated by the Dept of Transport for all TPH analysis, replacing the conventional laboratory Method 8015 procedure. This demonstrates the reliability of the data produced by the QED.

Taking a higher number of samples on site using the low cost QED ensures that any changes in hydrocarbon type and concentration across the site are identified. As few as 5% of these samples are typically sent to an accredited laboratory for confirmation, with data from the SI also useable for confirmation. The higher sampling density satisfies the criteria for statistically representative sampling outlined in WM3 without a significant cost.

The WM3 recommended Compliance Testing program can now be devised that uses the QED to confirm that the wastes have not changed during the excavation and that the hazard classification is correct for the soil being sent for disposal or treatment.

By having an initial higher sampling density, the volumes of soil that fall into the clean, contaminated or hazardous classification can be more accurately calculated, reducing the cost of disposal/treatment and follow the guidance on waste minimisation in WM3.

Real time analysis is also the best way to efficiently manage soil excavation and treatment, contributing to a lower overall project cost and lower environmental impact.

The QED is available for hire. It is easy to use and can be operated after a few hours of training. The cost including hire charges and all consumables is under £20 per sample, even if only 10 samples per day are analysed making the QED very economic. The cost per sample reduces as more samples are analysed per day.

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