Scottish Water was slapped with a fine of £6,500 this week after chlorinated water leaked from a reservoir killing more than 1,000 fish.
The fine was dished out at the Alloa Sheriff Court on Monday.
Scottish Water pled guilty to causing pollution at the Alva Burn waterway in the central Lowlands, after staff carried out repair work to a nearby reservoir August and September 2013.
Environment officers were alerted to the dead fish by members of the public according to the Scottish Environment Protection Agency which said it will take several years for the fish stocks to naturally regenerate.
Callum Waddell, SEPA’s investigating officer, said: “This pollution could have been avoided if sodium thiosulphate had been on site, with appropriate apparatus to treat the water before it was discharged.”
He added: “Scottish Water staff ought to know what to do in situations like this, otherwise valuable time can be lost. In this case there was an ongoing discharge for three days, which resulted in the death of over 1,000 fish and the local community couldn’t use the area downstream of the discharge for a variety of recreational activities, including fishing, swimming, paddling and walking.”
A Scottish Water spokesman said: “Scottish Water takes its environmental responsibilities very seriously. We have repaired a faulty valve at the reservoir to reduce the risk of this happening again.”