The damage caused by Marshalls Mono Limited affected more than two kilometres of a West Yorkshire watercourse.

Marshalls has permission from the Environment Agency to discharge effluent from their Sovereign Quarry site in Shepley into a tributary of Shepley Dyke.

However, on 13 March last year a discharge by the company contained more than 10 times the permitted level of suspended solids – material which can be dangerous to fish and other creatures around the water.

Samples of the watercourse showed the level of suspended solids to be 485 milligrams per litre, compared to the permitted level of 40 milligrams per litre.

The company, based in Huddersfield, yesterday (21 April) pleaded guilty at Huddersfield Magistrates’ Court to one offence of breaching its discharge consent.

Magistrates fined Marshalls £3,000 and ordered it to pay prosecution costs of £4,098.09 and a victim surcharge of £15.

Trevor Cooper, for the prosecution told the magistrates’ the alarm was raised by a member of the public, who reported the tributary was a milky brown colour.

Environment Agency inspectors then visited the watercourse and could not see the bottom of the stream, even though it is only 30cms deep – this discolouration of the water was visible for more than 2.2km downstream.

Mr Cooper told the court the pollution could potentially have harmed plants, fish and invertebrates.

The company had admitted the offence in interview, when it said it had stopped pumping because the discharge was “not clean”.

However, Marshalls took no steps to stop the discharge from continuing to enter the watercourse.

Mr Cooper said Marshalls’ previous record was an aggravating feature – the company received warning letters from the Environment Agency about discharges from Sovereign Quarry in October 2006 and January 2007, and in October 2003 was fined after admitting three offences of polluting groundwater with effluent.

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