Coal tar is a by-product derived from coal during the manufacture of domestic town gas. It was commonly used in the UK as a binding agent for aggregate in the construction of highways, car parks and paving until the 1980's when North Sea gas was introduced and town gas works closed. Bitumen was then adopted as the binding agent for macadam and top dressings.
Coal tar can have a high concentration of carcinogenic material such as benzo(a)pyrene and many other polynuclear aromatic hydrocarbines (PAH’s). This means it is potentially hazardous to human health (a potential cause of cancer) particularly when mixed with other materials such as asphalt waste.
Because of this risk to human health, it is obligatory to carry out tests before digging up such material. These tests will determine:
- The identity and composition of any PAH’S.
- Whether it is to be classified as waste coming under the Hazardous Waste Regulations 2005.
- Whether the material can be re-used or has to be sent to a specially designated landfill site for hazardous waste.
Needless to say there are substantial financial implications resting on the outcome of such tests. It is strongly recommended that early discussions are held with the Environmental Agency and local planning authority following the removal and testing of cores to establish a strategy for maximum re-use and to avoid disposal to landfill.
If the Environmental Agency agrees to its re-use it can be re-processed at a registered and approved facility as aggregate in a bitumen bound material such as a cold mix asphalt. The treated asphalt waste containing coal tar will have to meet the Specification for Highways Works 900 Series (clause 948) and 800 series (clause 810 to 880).
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