Coal Tar – What is it and Why is it So Bad?
A growing concern in the waste industries is the presence of coal tar in tarmac road surfaces. With more discovered every day, it seems as though the job of safely removing or remediating it will never be completed. In fact, utilities companies alone excavate and repair over 2.5m holes in roads and pavements each year. A daunting job, indeed.
Before the 1980s, tarmac binders and surface courses were derived from coal tar, which is formed as a by-product during the production of coal gas. This is now classified as a hazardous substance under WM3 rules. Since the 80s, petroleum bitumen (made from crude oil) has been used instead, as it is a non-hazardous material and can be recycled, collected and run back through the system safely.
WM3 has specific rules for tarmac waste containing coal tar. Waste is considered hazardous if it contains more than 0.1% coal tar or any coal tar present showing within Benzo a Pyrene being above >50mg/kg.
Why is it hazardous?
Coal tar is a class 1 carcinogenic substance (it can cause cancer). Encapsulated in the ground, it’s generally safe to walk over. The problem arises when road surfaces are damaged or worn away, where it becomes a big risk that needs to be dealt with. Older road surfaces are more likely to contain coal tar. However, some newer roads may have been overlaid onto a coal tar surface, so these cannot be disregarded as potential sources of the substance. As it poses a risk to both health and the environment, it’s important that road surfaces containing coal tar are dealt with appropriately.
How to deal with roads containing coal tar
The first step is to identify which surfaces contain coal tar. Core testing involves taking a sample and sending it to a lab for testing. This is a slow process that can take weeks. An alternative to core testing is using PAK spray paint to identify the presence of coal tar. The PAK spray paint reacts with hydrocarbons found in coal tar, changing colour from white to brown or yellow if coal tar is present. The process takes no longer than 15 minutes and can be carried out at different layers of road surface. It’s important to note however that the spray only detects the presence of coal tar and not concentration. This will require further investigation.
If coal tar is present, the options for handling it are few. The first is to leave it in situ. In its tarmac-bound state it is relatively inert. Overlaying it is an option. However, this isn’t always practical, depending on several factors.
Another method for dealing with coal tar is bituminous foam treatment. This encapsulates the material, allowing it to be reclassified as Cold Recycled Bound Material. It can then be used as a base layer.
The final option is to excavate the material and dispose of it as hazardous waste.
B&A Group can remove tarmac containing coal tar under Hazardous consignment notes to a dedicated treatment facility. The hazardous material is received, stored, treated and reused safely and in line with our environmental and sustainability principles, so we can provide you with the assurance that this hazardous waste stream will be dealt with responsibly and at a very competitive price.
If you have any questions on coal tar or would like B&A Group to run a site review please don’t hesitate to call us.