Land Contamination: Technical Guidance on Special Sites: Acid Tar ...

Box 2.5 Scenario: Acid tar disposal lagoons (continued)By this time, disposal to formal landfill sites was not practicable, due to thereluctance of waste disposal operators to accept acid tars and a correspondingincrease in price per tonne by five times over the three years. The finalmethod chosen involved in situ treatment using quicklime to neutralise theacid tars together with Fuller’s Earth. After the tar and quicklime had reactedand settled down (releasing a considerable amount of heat and steam), thetreated material was re-deposited in layers, compacted, covered with subsoiland landscaped.This second, in situ, remedial exercise took six months, twice as long as thatof three years previously where the wastes were taken away. The area whereacid tar wastes remained became a recreation ground whereas the otherremediated areas where the tars were removed and replaced with limestonewere redeveloped for light industrial units. The remediation by quicklimeappears to have been successful, although generally the method of dispersionby chemical reaction was considered preferable. Similar treatment methodsat another site were less successful, and should therefore be subject totreatability trials.The principal receptors of concern were:• human health – associated mainly with the highly corrosive acidicconditions and also the physical hazard of fires and unstable ground;• groundwater and surface waters – particularly from mobile oils anddissolved phase contaminants;• adjacent buildings and infrastructure – due mainly to the instability ofthe lagoon, mobility of the tars that had broken through to the surface andfire.R&D <strong>Technical</strong> Report P5-042/TR/04 14