Appearing before Chesterfield magistrates on 29 April, the company pleaded guilty to causing polluting matter to enter controlled waters, contrary to section 85(1) of the Water Resources Act 1991. It was ordered to pay £1,551 costs.
On 21 November last year, Agency officers were called to a tributary of the Rother in Clay Cross because it was black. The officers traced the pollution to DS Smith's factory next to the river.
At the time of the incident, the company was carrying out repairs to its trade effluent system and was storing untreated ink washings in on-site sumps.
Sometime before the incident, a non-return valve had broken in a pipeline leading from the sumps. This allowed ink
washings to enter the tributary and eventually the Rother itself.
Although there was no evidence of fish deaths, samples taken from the river showed the discharge to have a high biochemical oxygen demand.
In mitigation, the company said it had replaced the broken valve as soon as it was told of the incident. It also now checks outflows daily, has appointed a health, safety and environmental manager, and has given five employees environmental training.