Bill McGrath, chairman of Ingol Community Association, raised the alarm and reported the issue to a local councillor saying he feared it could be a hazard.
The colourful luminous looking concoction appeared in a stream off Cottam Lane a few days ago.
He said: “Although at present the water is only just flowing when it rains this will eventually find its way into a stream that flow into the Lancaster canal. I’m not sure what it is but looks colourful.”
Bill, of Barry Avenue, Ingol, says this is the latest in a series of problems with fly tipping alongside the popular unadopted bridleway.
He claimed: “If you walk from the Barry Avenue side look out for the couple of tons of fly tipping on your left hand side which Preston City Council cannot remove as they don’t seem to know who owns the land. If you approach from the Railway Bridge side if you look to the left you will see about a dozen or so black bags in the trees that the council cannot remove.”
He noted there also car tyres in the stream and said: “It makes a mockery of ‘keep you neighbourhood clean’.
But Ingol Councillor Pauline Brown said the council is investigating the issues and is aware of the problems. She was planning to visit the brook site on Tuesday and said she shared concerns about whether the stream had been coloured with something toxic. She said: “The council is trying to find out who the land belongs to so they can deal with it.”
A Preston City Council spokesman said: “While the green water is an Environmental Agency issue, it is our belief that it is simply some drain tracing dye, a non-toxic liquid used by various agencies and organisations, which has made it into the water.
“The fly-tipping is on unregistered, private land. An investigation is underway to determine who owns that land so that we can instruct them to remove the waste.”