Thames Water Utilities Ltd has pleaded guilty to polluting a controlled watercourse—Dagenham Brook—on 8 August 2005 with poisonous, noxious or polluting matter under section 85 of the Water Resources Act 1991.
Thames Water had failed to maintain storm tanks which allowed sewage to pour into the river through holes in the joints between precast concrete sections which made up the tank walls. These joints contained a sealing compound, which had failed in a number of places.
The sewage contaminated nearly two miles of the Dagenham Brook, which then discharges in the River Lee at New Spitalfields Market, in Leyton.
The impact on the river was significant; the river was a cloudy grey colour and there was a strong sewage smell along the affected stretch of the river. Dissolved oxygen levels in the river at Leabridge Road were recorded as 2.4 per cent. The minimum level of dissolved oxygen necessary to sustain fish life is typically around 25 to 30 per cent.
A fleet of tankers worked for three days to remove the sewage from the river at two locations, Orient Way and New Spitalfields Market, in Leyton, which although failing to reduce the impact on Dagenham Brook did alleviate the problem in the River Lee.
Once the storm tanks were identified as the source of the pollution Thames Water began to drain them down to prevent further pollution.