A chemical plant has been ordered to pay £16,000 in fines and costs after acid leaked into a river.
The court heard vegetation turned black and fish died in the leak at Kingsweston Rhine and a pond near the Rhodia Organique plant in Avonmouth.
The firm pleading guilty to causing poisonous or polluting matter to enter controlled waters and failing to maintain its equipment.
Since the leak in July 2004, Rhodia has added a pH probe and visual checks.
Bristol Crown Court fined the chemical plant £10,000 and ordered it to pay £6,000 in costs.
Sara Galpin, of the Environment Agency, said: “The company didn’t notice the problem until we brought it to their attention.
“The level of hydrofluoric acid was 18 times the amount needed to kill a stickleback. Any company that manufactures such highly dangerous chemicals should have anticipated the possibility of such a leak and implemented far more stringent checks.”
The spill happened after a valve on a pipe leading from the effluent treatment plant dropped off due to poor maintenance.
The Environment Agency was called after dead fish were seen floating in the waters. The next day, Rhodia confirmed that they had found a leak of hydrofluoric acid and started pumping water from the Kingsweston rhine back to their effluent treatment plant.
Rhodia also took contaminated water back to their site in tankers to be treated. It took 20 days to return the waters to normal pH levels.
The company has now installed a probe at the outfall to alert staff to any problems and a walk-by programme of visual checks on the pipeline network.