A STREAM became very acidic after a leak from a dyeworks, a court heard.
Harrison Gardner, of Victoria Dyeworks, Hightown, Liversedge, admitted causing sulphuric acid to enter Clough Beck on or before last December 20.
Dewsbury magistrates fined the firm £1,000, with £799 costs for the Environment Agency, which brought the case.
The court heard that between December 15 and 19 Yorkshire Water Services officials investigated complaints of sulphide smells in the area.
They eventually found there was an acid discharge into the surface water sewer.
A reading of 0.5 - very acidic - was recorded on a small stretch of the beck.
People living nearby were warned to stay away from the beck, which runs between two gardens and can easily be reached by the public and animals.
Environment Agency officers went to the area on December 19 and confirmed that the watercourse at Hare Park Lane and 700 metres downstream at Clough Lane was strongly acidic.
The source was traced back to a tank at Harrison Gardner.
A tank had failed and an embankment had failed to prevent a leak.
Director David Harrison said sulphuric acid had been lost.
The court was told the tank had now been removed and the area where it was had been cleared.