South East Water’s Operations Director Douglas Whitfield said: “Following investigations we can confirm human error led to some sediment from a water cleaning process and not sewage being released from our lagoons into a ditch leading to the Andrews Stream, Barcombe.
“We are sorry this has happened and have been working closely with the Environment Agency.
“We have already put a range of measures in place to prevent this happening again.
“As far as we are aware the incident happened on June 12 only and the problem was put right immediately with the Environment Agency alerted straight away.
“We know about the sensitive fish spawning habitats in the Andrews Stream and of the improvements which have been carried out to this watercourse over the years.
“We wouldn’t knowingly discharge sediment into this system at any time of year, although we do have a permit for a discharge of clear water from our settlement lagoons this is controlled in line with the Environmental Permit issued by the Environment Agency.
“We take our responsibility to protect the environment very seriously. We have a dedicated Environmental Team which works hard to make sure the supply of safe drinking water has the least impact possible on nature, wildlife and the communities we serve.”