There was a sewage pollution incident in the Beverley Brook on Friday 26th September. The water in the brook was visibly different, darker and cloudier than usual. The source of pollution was upstream of Wimbledon Common. Our volunteers took a water sample for E.coli testing from the brook at Palewell Common where the bulk of the pollution travelling downstream was observed at that time. Our E.coli tester showed a value of 68,000 cfu (colony forming units) per 100mL that is 30-60x more than our recent readings of 1000-2500 at Barnes Green. For rivers with bathing water quality this number needs to be under 900 for sufficient water quality, and under 500 for excellent water quality.

The Environment Agency has been investigating the sewage pollution incident and their officers have been working with partners on site and have taken water samples to assess the impact.

According to the EA, “whilst there was some visual discolouration in the Beverley Brook at Barnes, there were no signs of fish or wildlife in distress, and water quality was normal. The primary impact is discolouration, and we expect this to disperse naturally in the next couple of days. No ecological impact is expected.”

We are hoping that the pollution will completely disperse over the coming days and won’t have an impact on the local wildlife at Barnes Common nature reserve. Once the water quality has returned to normal, we still need to point out that the water may look clear, but we receive reports from time to time that dogs and children, as well as adults, have become sick after exposure.

The water in Beverley Brook is not designated as of bathing quality, nor is it monitored regularly. Its main water source is treated water from the Hogsmill sewage treatment plant.

Many of us are working to improve the habitat and water quality and we are delighted that water quality has improved in recent decades. In the past year we have recorded nine species of fish but, good as this is, these species are relatively resilient to poor water quality.

Please note:

• Recent surveys have shown that there are many drain misconnections introducing sewage into the brook – severe cases are reported when identified but can take up to 3 years to be resolved, as tracing the source and correcting it can be complex.
• The brook also has four Combined Sewer Outfalls where authorised discharges of untreated sewage can take place without notice – for details you can check the Thames Water website.
• Recent tests have also shown high levels of chemicals of emerging concern, including parasiticides, anti-depressants and ‘forever’ chemicals, most likely from treated wastewater discharged to the brook.