As you mentioned that it’s following a ditch, it sounds like it’s a deliberately dug overflow system from the old pit. I presume there is some form of slag heap that the water is leaching from, hopefully DEFRA can test the water soon and determine the level of risk from the overflow and also look at remedial action.
This is a SSSI Protected site for rare water plants , hopefully environment agency, together with Canal river trust and Natural England will take action to stop this .
