The case was brought by the London Borough of Camden for two incidents of serious dust pollution in January 2002. The site imports aggregates by rail and mixes them with cement. The concrete mix is distributed around London.
On 22 January, an environmental health officer inspecting a neighbouring site noticed large emissions of dust from the Hanson works. He decided that it was potentially harmful to people in the area.
The officer, Peter Carey, told ENDS that following the incident he gave Hanson a verbal warning. He said that he received an assurance that it would not happen again.
On 28 January, Mr Carey saw an even larger dust cloud which "looked almost like there had been an explosion."
Mr Carey said that the emissions were probably caused during the off-loading of cement from a lorry when the driver may have over-pressurised the silo, resulting in a discharge of dust. Hanson has since installed valves on the silo to prevent excessive pressurisation.
At Highbury magistrates court on 5 November, Hanson pleaded guilty to six offences under section 23(1)(a) of the Environmental Protection Act 1990. It was fined £2,000 for each of three offences on 22 January, and £4,000 apiece for a further three on 28 January. Costs of £3,116 were also awarded against the company.
The offences related to breaches of the conditions in Hanson's authorisation under the local air pollution control (LAPC) regime - that there should be no visible emissions across the site boundary, that the authority should be notified and records made of any polluting releases, and that staff should properly monitor deliveries to the site.