Environmental Pollution Incidents (EPI)
What are Environmental Pollution Incidents?
Environmental Pollution Incidents (EPIs) are reportable events where a watercourse is polluted via Scottish Water infrastructure.
Most incidents stem from issues within the sewer network, but they may originate from any waste water or drinking water asset.
Scottish Water has an obligation to report each incident verbally and in writing to SEPA, to meet regulatory requirements set by the Water Industry Commission.
By working closely with SEPA and by identifying best practice, Scottish Water can continue to improve Scotland’s water environment.
EPI Progress 2024 - 25
EPIs and our progress to reduce these are recorded in our Annual Report and Accounts: Performance and Prospects.
Annual ReportEPIs are categorised through review and agreement by SEPA:
- Category 1: Major effect on the environment; extensive visible pollution or littering; impacting people, property, or water quality (e.g. closure of a bathing water beach)
- Category 2: Significant visible pollution or littering; less impact on the environment, people and property, or water quality; with a reduction in amenity
- Category 3: Minimal visible pollution or littering, causing minor impact on the environment, people or property, with a limited or localised effect on water quality
Caring for the Environment
We're working hard to reduce the number of Environmental Pollution Incidents
Overflows and EPIs
Routine overflow events from our network and treatment works overflow structures are not considered EPIs if they are working as they are intended.
These include Combined Sewer Overflows, Settled Storm Sewage Overflows, and Emergency Overflows (CSO, SSSO, and EO).
These overflows are designed to prevent flooding at our assets, communities, and homes, removing excess surface water from extreme weather events to prevent sewers from becoming overwhelmed.
Around 99% of overflows are rainwater, surface water, road run-off, grey water, infiltration of groundwater, and trade effluent.
EPIs may be caused by overflows when chokes or collapses occur at the overflow rather than in the sewer network.
You can find out more at Overflows Explained.
Overflows
Visit our overflow pages to find out why they are vital to help prevent flooding.
OverflowsWhat are we doing to reduce EPIs?
At Scottish Water, we operate thousands of water and waste water treatment works, pumping stations, and tens of thousands of miles of water and sewer pipes.
We manage our assets with a focus on preventing environmental impacts, but EPIs can still occur.
Most EPIs in the sewer network are related to blockages caused by sewer-related debris such as wipes and sanitary products, while others may be due to faults at an asset.
Enhanced monitoring and improved processes are allowing our teams to react more quickly to blockages, significantly reducing the more serious Category 1 and 2 EPIs.
Increased real-time monitors at our overflows is helping us to identify EPIs by using the data to take action early and prevent or significantly reduce any impact.
Our Improving Urban Waters Routemap sets out our ambitions to increase our use of data-driven insights to become more proactive in preventing incidents.
