Every day, we collect over 900 million litres of waste water through over 50,000 km of sewer pipes. This network also includes 2,200 pumping stations and contains around 4,000 combined sewer overflows.
Occasionally the sewer system fails, leading to pollution of the environment or flooding of our customers’ properties. Customers have told us they want us to prioritise the prevention of flooding internal properties with sewage.
The majority of sewer flooding incidents are due to blockages, often caused by disposal of items such as nappies, sanitary items, wipes and cooking oils. They can also be caused by too much rainwater entering sewers. This problem is growing because of the increasing rainfall intensity associated with climate change, increased paving in urban areas and the impact of new development. We must therefore take the most sustainable approach to managing rainwater.
We have developed a storm water strategy of 'No more in, what's in out'. This means we want to ensure our sewer network collects as little rainwater as possible, so we can maintain the capacity in our sewers to allow us to safely convey waste water. We aim to remove rainwater from our sewers by diverting it to more sustainable routes via the use of surface water systems and blue-green infrastructure such as sustainable urban drainage systems (SUDS). In order to deliver this more sustainable approach to managing storm water, we will work with our partners including planning authorities, and champion the transformation of the management of surface water in Scotland.
We will continue our industry-leading approach of requiring developers to install sustainable urban drainage systems for new developments, which we will then adopt and manage.
Working with SEPA, local authorities and the Scottish Government, we will deliver integrated catchment studies to develop surface water management plans and exemplar schemes for storm water removal. We will seek to influence public policy to drive changes that will support effective surface water management.
We can no longer rely solely on traditional engineered solutions, such as making our sewers and tanks bigger. These methods are costly, disruptive, carbon intensive and use significant resources, while delivering only limited additional capacity.
We will increase sewer capacity only where there are existing flooding issues, and storm water removal is not feasible for us or our partners. In these circumstances, we will invest in engineering solutions to protect customers from flooding at the lowest possible cost. We will use the latest hydraulic models to understand where the risk of flooding is highest, to help prioritise investment and build assets that will be fit for the future.
We will continue to use behavioural campaigns to inform customers that flushing away un-flushable items can cause sewer blockages. We will work nationally with partners, such as Zero Waste Scotland and Citizens Advice Scotland, as well as with European partners, to push for the correct labelling of un-flushable products currently labelled as flushable. Alongside this, we will continue to put into action a planned sewer cleaning programme to prevent blockages, and explore new methods to actively manage our sewer capacity.