A Thames Water spokesman says the water is not sewage.
They say it is the result of a burst water main, which had mixed with silt and mud.
Engineers are on site working to manage the problem.
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Police were called to a fight between two groups of people on the petrol station forecourt at Cobham services.
The barriers are part of a series of measures put in place by the Metropolitan Police.
Resident group Justice 4 Grenfell say they were not consulted and will raise concerns about the appointment at the highest level.