It is regrettable that pollution can sometimes be seen floating on the surface of the Avon New Cut following periods of heavy rainfall.
There are several drainage outflows along the banks of the New Cut. The majority of these discharge ‘clean’ surface water directly into the river. However, much of the sewer network is ‘combined’ (ie foul sewage and rainwater are carried in the same sewer pipes). The contents of these combined sewers is ordinarily pumped to a sewage works for treatment.
The aged sewerage infrastructure cannot cope with the increasing number of heavy downpours and continuing urbanisation of the city. Information published by Wessex Water informs us that sewage flows through the Ashton Avenue sewage pumping station during dry weather conditions at a rate of approximately 350 litres per second. During storm conditions, this can increase to more than 7,000 litres per second, which far exceeds the volume that can be conveyed for full treatment in the proper manner.
When heavy rainfall occurs, Wessex Water are permitted by the Environment Agency to discharge some diluted sewage into the New Cut in order to prevent pipes from backing up and flooding homes and businesses. Polluting waterways and flooding bathrooms with dirty water are both completely undesirable.
Alongside Wessex Water’s ongoing efforts to modify and increase the capacity of the network, there are measures that many of us can take to reduce the amount of rainwater entering the sewers, such as:
- Water butts: Connecting a water butt to one of your rainwater pipes is a great way to reduce the amount of rainwater entering the sewer network, and your garden plants will love you for it. If you already have a water butt, do you have space to install another? Be sure to make use of the rainwater on your garden plants after it has been collected, to free up space for more of this valuable resource before the next downpour.
- Front gardens: Across Bristol, front gardens have been dug up and paved over to create off-street parking or reduce maintenance, which has decreased the amount of ground available for surface water to soak into. Permeable paving and gravel are lesser evils. Better still, keep/restore your front garden and improve your kerb appeal.
- Soakaways: If you have a sufficiently sized garden, have you considered installing a soakaway? As well as reducing the amount of rainwater entering the sewer, you will also reduce your household costs because Wessex Water will apply a reduction to your bill.
Lots of people making small changes will result in a much larger effect. If every household with a yard or garden did their bit, the overall benefit could be huge!