Environment Agency Wales has launched an investigation after a 6.5 mile stretch of the River Rhymney turned orange.
Officials say the river, from Bedwas to Machen, has changed colour possibly due to a discharge from an old mine.
The Environment Agency has said the pollution entered the river from the Porset Brook, near Bedwas House Industrial Estate, and officers have been at the site since early Tuesday morning. The exact source will be difficult to locate due to the complexities of the underground mine workings.
Tests are being carried out to assess any damage to water quality and wildlife. If samples taken confirm it is caused by minewater, the Coal Authority will be asked to work with the Agency to try to improve the situation.
Discharges of this type can occur many miles from the mine, as drainage tunnels were dug over long distances.
A spokesperson from Environment Agency Wales said: “Our investigation has ruled out active industry within the area and we’re confident the pollution comes from minewater possibly due to an underground collapse in an abandoned mine.
“Minewater is often bright orange or brown because of the high levels of dissolved ferrous iron.
“So far, we haven’t noticed any signs of fish in distress, but we’ll continue to monitor the situation closely until the pollution stops.”
Caerphilly Observer reader Wendy Preece sent this picture in from near Machen.
This stream flows below the level and very near to the contaminated and highly poisonous former TAR PLANT, there is no doubt the water table levels would allow ground water to seep into the ground which feeds itself into this stream, it has potentially done so before.
The Tar Plant site contains all sorts of cancergenics and other serious contaminants, it is not a `secure` site in respect to water seepage and the escape of these potentially life damaging contaminants from the site getting into surrounding land and water courses.
The Caerphilly council and the Environment Agency, who have a regulatory and a statutory responsibility to the citizens of the borough to properly monitor the contaminants contained within this privately owned site should start their investigation there.
The owners of the site have indicated they want to redevelop the Old Tar Plant for `Housing`, is that a wise move?.
If its coming from the Porset Brook, at a guess its from the Clay Pit Area, this was mined extensively in the 19th century, and about 20 years ago the Clay Colliery Company wanted to opencast the area.At the time the ahd several boreholes and the water from them was red, due to the iron in the coal measures. There was another mine, the Rhos Llantwit, near the entrance to Lansbury Park, and work has been done recently to cap the shafts, but there was never any wateroutflow from that site.
Just an afterthought, since the last time I saw the river runing red was when the Clay Colliery Company were drilling boreholes, is this happening again and is someone trying to opencast the area?.