Anglian Water has been ordered to pay £94,000 after sewage contaminated a brook through an emergency overflow pipe.
More than 1,500 fish were also killed as a result, according to the Environment Agency. At the time of the incident in April 2011, three pumps at Ingrave Pumping Station stopped working over three years but no alarms were set off.
“At one point this left the pumping station with no operational pumps for 12 hours”, the Agency added.
Ms Sarah Le Fevre, Defence Counsel, said Anglian Water “deeply regretted” the incident.
Speaking after the case, Peter Cooke, Environment Agency Officer said: “This pollution was reported to us by a member of the local community who found the brook grossly polluted with sewage.
“It had a catastrophic impact on fish and was distressing for local residents who value the brook for its diverse wildlife.”