The Wandle pollution scandal isn’t going away

By - Tuesday 16th May, 2017

Now there’s sewage in the River Wandle

Pollution qued up and waiting to enter Wandle Park

Photo author’s own.

I recently wrote an article in the Citizen highlighting the issue of visible pollution in the River Wandle in Croydon. Since then I have carried out further investigations. What I have discovered is troubling.

After becoming aware of pollution in January 2017, I have walked the length of the river within Wandle Park almost every day. There has not been a single occasion when I could not see some visible contamination. Sometimes it’s just a smear of oil in a couple of places, but more often larger amounts are visible along the river channel. Sometimes there are very large quantities which would be visible to anyone who glanced at the water. The fact that fresh problems appear daily can make reporting it to the Environment Agency a challenge as it’s not always possible to determine what is a ‘new pollution event’.

The Wandle was declared an open sewer in the 1960s: biologically dead, nothing grew in it

I have now learned that since work was done to bring the culverted river back to the surface in the park in 2012/13, there has been been on-going contamination. From time to time, more serious events have occurred. When the river returned to the surface, its flow was made visible: it is not possible to know the state of the water during the years when the Wandle in Croydon ran underground, although it was officially declared an open sewer in the 1960s, meaning that it was biologically dead and nothing grew in it.

It is difficult to know if pollution is worse this year than in recent years. What is certain is that the pollution that is there must be more concentrated and visible because this winter has seen the lowest rainfall for twenty years.

Now that we are monitoring the situation closely, it is clear that the Wandle is being affected in three different ways.

Petrochemical pollution

There is on-going background pollution of this type (petrol and diesel) in the Wandle. It was this which was investigated by the EA earlier this year. Level were found not to be dangerous, at least at the times when testing was carried out. It appears to be caused by run-off from roads into drains which flow into the river (which would have been acceptable practice in the late 1960s when the dual carriageway, Roman Way, was built alongside Croydon minster close to Wandle Park). This drainage also brings with it pedestrian litter from the road, such as cigarette butts, chewing gum and the contents of car ashtrays. Whilst unpleasant and unsightly, it is considered normal to drain roads more or less directly into our rivers in this country.

Surface pollution trapped near the skate park.
Photo author’s own.

More serious sporadic petrochemical pollution has also occurred, such as that apparently caused by anti-freeze being dumped down a drain in January this year. We are also aware of a serious issue of pollution with red diesel which occurred in 2013 during the work to landscape the park around the new riverbed: luckily this was dealt with rapidly and effectively by the contractors who were working on site as the pollution first appeared. The random timing and varied nature of these major pollution events suggests that the cause is individual cases of illegal leakage or dumping. Leading angling writer and rivers expert Paul Dennis, also a Citizen contributor, confirms that based on his experience, these events have all the hallmarks of pollution by the drainage system.

Contamination with cooking oil

More or less continuously, cooking oil is also appearing in the river. Its large quantity and regularity suggests that the source is unlikely to be domestic and is probably one or more restaurants or fast food outlets. The substance must have been dumped illegally straight into a drain: had it gone down the foul sewer (via toilets, for example) – which would also be illegal – it would be dealt with at the sewage works. It is also possible that the cooking oil could have leaked.


Brown stuff with a very strong smell of excremen

Pollution with a very strong smell of excrement.
Photo author’s own.

On Friday 5th May, I smelt sewage strongly in Wandle Park. Nothing was visible in the water. Two days later, on Sunday morning, contamination appeared. It seemed to be excrement. The fact that the smell was present some time before its cause became visible suggests that the source was some distance upstream.

I reported the problem to the Environment Agency at once and a van from Thames Water arrived within hours. The Thames Water team dammed the river with sandbags just below the grid where it flows into the park. This action was effective, at least for the visible pollution; next day, the water downstream of the dam was clearer. But the contaminant build-up behind it was also very apparent.

The likeliest cause seems to be that someone had – once again illegally – emptied a septic tank or Portaloo into a drain. It’s also possible that the cause is industrial run-off, since without testing we cannot be certain that the waste is of human origin. However, the fact that a used sanitary towel appeared on the bed of the Wandle at this time seems suggestive of this.

Very strong smell of sewage 7th May 2017

Very strong smell of sewage on Sunday 7th May 2017.
Photo author’s own.

Furthermore, despite Thames Water’s sandbag dam, pollution was again visible along the length of the river within Wandle Park on Sunday 14th May.

On Monday 15th May, with the arrival of rain, the river in the park appeared much clearer. Unfortunately, with the rising water level, it looked as though a large backlog of pollution was about to top the bar at the bottom of the entry grill and flow on down into the park. After eleven continuous days, the smell of foul sewage was still quite strong.

Large structural crack inside the storm drain

Large structural crack inside the storm drain.
Photo author’s own.

These are not the only problems affecting the River Wandle. The network of mostly underground pipes forming the upper section of the river stretches uphill from Wandle Park as far south as Caterham and Coulsdon under various names including Caterham Bourne, Merstham Bourne and the Old Bourne Flow. The underground section is in a poor state of repair; this includes the section from Wandle Park past the minster and on to the flyover, built in the late 1960s.

Just a few metres inside the storm drain where the Wandle enters the park is a six metre long crack in the reinforced concrete wall big enough to put your hand in. I reported this to Croydon Council which passed the information on to the Environment Agency.

At the pedestrian underpass in front of the minster, the pipe containing the Old Bourne Flow, built in 1968, has been leaking for over thirteen years. In 2004, following complaints from local residents about having to walk through pools of green slimy water in the underpass, the council carried out repairs, cutting a groove across the width of the footpath to a drain on the other side and putting a grid drain into the groove. Water still leaks onto the footpath at either end. Even thirteen years ago, the water leaking from the Old Bourne Flow must have been polluted because the green slime requires nutrients, i.e. pollution, to grow.

Old Bourne Flow leaking into the underpass

Old Bourne Flow leaking into the underpass by Croydon minster.
Photo author’s own.

In my view, back in 2004 it would have been advisable to dig up the footpath above at ground level and repair the leaking pipe. Instead, a groove was cut across the subway footpath, diverting the polluted water from one side to the other. For the last thirteen years, meanwhile, water leaking from the pipe containing the Old Bourne Flow has continued unseen, undermining the footpath and Roman Way.

These discoveries call into question the quality of the concrete used in the original building work. Indeed, the retaining wall to the dual carriageway on the ramp in front of the minster shows visible concrete rot in several places. Worryingly, I have also learned that Thames Water and the Environment Agency do not have an accurate map of the pipes leading into the Wandle.

As well as concerns about the effects of pollution on wildlife, the health of the river and the state of the infrastructure surrounding it raise issues of public health which I believe should now be addressed.

Peter Ball

Peter Ball

Peter Ball moved to Croydon three years ago. He's a mathematician and former full-time communard hippie, architectural draftsman and planning technician for the Peak District National Park. Nowadays he's a partner in a translation company and a computer consultant. 'Quite conventional and boring sort of bloke', although his description of himself, is not the view of others.

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  • FishFace

    I assume the ‘anti-freeze’ you are referring to is in the photo on your first article where the Wandle is green in colour? This is not anti-freeze but a harmless dye that is used when tracing drainage networks. This suggests that someone (possibly the EA or Thames Water) were investigating the route that the drains take within the culvert.