What is the Managing Reclaimed Asphalt Guidance?
The Managing Reclaimed Asphalt – Highways and Pavements ADEPT Guidance note is intended as an aid to classifying and reusing arisings from bituminous bound road materials. The main aim is to reduce the amount of hazardous, or non-hazardous waste being sent to landfill, or for incineration, and allow industry to reuse as much of this valuable material as possible, when road materials are replaced.
From January 2016, the Managing Reclaimed Asphalt – Highways and Pavements guidance version 2016-1, has been updated to bring it in line with the latest technical guidance on the classification and assessment of waste, WM3.
It is worth noting that the guidance note supersedes the December 2013 version, which is now withdrawn.
How does WM3 affect the guidance?
WM3 sets out in detail how hazardous waste is classified against hazard statement codes. Road tar contains chemicals that are carcinogenic (HP7), ecotoxic (HP14), or both.
The author of the guidance has noted that the hazard that results in the lowest limit is HP7, Carcinogenic. Coal tar that is included in road tar is therefore classified as hazardous on the updated List of Waste (LoW), a legal classification system for those who need to identify different types of waste and their potential hazards. The updated information within WM3 has therefore been used to formulate the testing guidance that Managing Reclaimed Asphalt offers.
What else does the guidance include?
The guidance covers a large amount of detail around classifying and reusing arisings from bituminous bound road materials. To save you time, the main points are summarised below:
Road tar is a complex mixture of hydrocarbons; some of these have been shown to be carcinogenic, others are toxic to aquatic life, some are both. Road tar is processed from coal tar and does not contain all of the chemicals that are present in unrefined coal tar. However, coal tar and many tar derived products, are classed as carcinogens. Consequently road tar must also be considered a carcinogen, even though it may contain fewer hazardous compounds than untreated coal tar.
The excavation process
Road materials require replacement occasionally for a variety of reasons. In the removal process the existing material is milled out using a powered device and the arisings are collected for disposal, or ideally, re-use. The removal is a construction process, similar in nature to demolishing a building.
Coal tar can be hazardous to humans, particularly through inhalation and ingestion of dust at ambient temperatures. Dermal exposure is also a pathway for tar products, and therefore personnel should avoid handling road planings.
The Environment Agency Position
According to the guidance, in the UK, the three Environment Agencies generally take the view that all arisings from construction processes should be classed as waste. As such, anyone carring these materials, recycling them, or reprocessing them must possess all appropriate permits and licences.
Testing for Coal Tar Products
It is vital that any samples presented for analysis are representative and homogenous.
In detecting tar products, two tests are usually used:
- Speciated PAH analysis (PAH 16)
- Phenols and cresols (either by speciated analysis, or by phenol index)
Screening for PAH
It is possible to use a spray product, called a PAK marker, specifically designed to detect PAH. However, PAK spray can give false positive results. Other screening methods, for example, acrylic white paint spray, can be used but should be calibrated against analytical methods for PAH.
Leaving tar bound material undisturbed is acceptable without testing for leachate potential – it therefore never becomes waste and is the highest level of the waste hierarchy. Leachate testing may be needed if the material is to be disposed of in landfill. The leaching properties, as required, by the appropriate WAC test, would then need to be established.
If an investigation has not been carried out and the planings are not characterised then the planings must be tested instead.
Prior to any excavation operation for a highways project, it is recommended that an investigation is carried out to establish the location of any tar contaminated material, the properties of the in situ material and the anticipated properties of any excavated material. An investigation into existing road conditions, using the likes of road coring analysis, and the assessment of the properties and quality of the arisings are essential to achieving proper re-use of the excavated material.
To assess the nature of the arisings the variability of the source material must be considered. Road cores should be nominally 150mm diameter and taken at between 25 and 50 m centres. A minimum of three cores should be taken unless the site is less than 30m2 when one core is adequate. A road core sampling plan should be made and recorded including the details of the decisions made.
The investigation project manager should have sufficient experience of highway investigation and be familiar with the relevant legislation, as well as the full Managing Reclaimed Asphalt guidance.
Any treatment chosen must meet the engineering demands of the specific road and there are a number of options available:
- In situ stabilisation
- Non hazardous sites
- Hazardous sites (including prevention, preparing for re-use, disposal – as a last resort, and other recovery)
Health & Safety
A proper assessment of the hazards associated with handling asphalt arisings should be carried out, which should include a full COSHH assessment.
Considering the Environment
As well as posing a risk to human health, PAH found in coal tar, can affect other organisms.
The Managing Reclaimed Asphalt Guidance summarised in this ‘Hot Topic’ was written by John Booth of SOCOTEC on behalf of ADEPT. Additional input was provided by Robert Gossling of Lafarge Tarmac and by the Mineral Products Association.
How SOCOTEC can help
SOCOTEC is one of the UK’s leading providers of bituminous testing and advice and can offer support on your project.