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Cressacres Carp Syndicate | River Chess- Sewerage discharge warning

10th May 2014

A murky sample of river water downstream of the sewage treatment works

Courtesy of the River Chess Association website:

Thames Water has been discharging "storm sewage" from the Chesham Sewage Treatment Works into the River Chess continuously for over 5 weeks. Regulations allow the company to do this under storm conditions, but the current releases are the result of high levels of groundwater. Thames Water agrees that this is the case and we believe that this type of discharge is not covered by storm sewage consents. We have made this position known to the Environment Agency.

Unfortunately Thames Water have few options in these circumstances. They could truck the sewage away, but all their sewage works are running at maximum capacity. The alternative is to allow sewers to back up and flood homes, or they can discharge to the river. Of course, the latter alternative is used.

The fishery below the sewage outfall pipe at Blackwell Hall is seeing dead fish in the river and this is a worrying new development which has been brought to the attention of the Environment Agency. We hope to recover some of these dead fish this week for examination.

Many of the sewage treatment works across the whole Thames Water region have now stopped discharging sewage into the rivers, but we can confirm that the Chesham works is still discharging, making it one of the worst offenders. We are not aware of any occasion where a discharge into the Chess has continued for so long. Last year, we had many intermittent sewage discharge events, but none were continuous.

Fly monitoring volunteer in protective equipmentOn the 28th March we sampled invertebrates in the Chess at a point just below the outfall pipe as part of our monthly riverfly monitoring programme. The result obtained was just above a trigger level that would result in an Environment Agency investigation. We did a comparative study above the sewage outfall pipe and obtained a substantially higher score (12 compared to 9), which included more than 20 mayfly Danica nymphs, one of the least tolerant species to pollution in a chalk stream. These were absent in the sample below the outfall pipe.

The Chess could be two different rivers above and below the outfall pipe, the one above is clean and clear with chalk stream plant life, bullheads and varied invertebrates, the one below is cloudy, choked with sewage fungus and lacking key chalk stream species.

The problems at the Chesham Sewage Treatment Works are a result of years of underinvestment. In normal conditions, the plant is working close to capacity. The slightest stress placed on the plant results in equipment failure, tanks overflowing and discharges. Over recent years Thames Water has increased buffer storage by 160%, but this is still inadequate. A significant amount of additional housing is planned for the Chesham area in the coming years, which will lead to a need for greater sewage capacity. Only recently has this begun to be addressed.

We understand that Thames Water has few options to resolve the immediate problem. However, we are working with Thames Water and the Environment Agency in the hope that a robust investment plan can be agreed that deals with the problem of capacity and groundwater ingress at the Chesham Sewage Treatment Works.

A number of school events connected with the river which we had planned have had to be cancelled because of pollution concerns, including the release of trout parr from our Trout in the Classroom programme.

We would recommend that everyone keeps clear of the river downstream of Blackwell Hall Lane. We would also suggest that all pets are kept out of the river.

All pollution incidents should be first reported to the Environment Agency Hotline on 0800 80 70 60. In the case of sewer leaks in our area also contact Thames Water on 0845 9200 800.

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